Fixes crashes from loading mods without an eras.json file (#4910)

core/src/com/unciv/logic/city/CityStats.kt

@@ -127,7 +127,7 @@ class CityStats {
             if (otherCiv.isCityState() && otherCiv.getDiplomacyManager(cityInfo.civInfo).relationshipLevel() >= RelationshipLevel.Friend) {
                 val eraInfo = cityInfo.civInfo.getEraObject()
 
-                if (eraInfo.friendBonus[otherCiv.cityStateType.name] == null || eraInfo.allyBonus[otherCiv.cityStateType.name] == null) {
+                if (eraInfo == null || eraInfo.friendBonus[otherCiv.cityStateType.name] == null || eraInfo.allyBonus[otherCiv.cityStateType.name] == null) {
                     // Deprecated, assume Civ V values for compatibility
                     if (otherCiv.cityStateType == CityStateType.Maritime && otherCiv.getDiplomacyManager(cityInfo.civInfo).relationshipLevel() == RelationshipLevel.Ally)
                         stats.food += 1

core/src/com/unciv/logic/civilization/CivInfoStats.kt

@@ -86,11 +86,15 @@ class CivInfoStats(val civInfo: CivilizationInfo) {
         for (otherCiv in civInfo.getKnownCivs()) {
             if (otherCiv.isCityState() && otherCiv.getDiplomacyManager(civInfo.civName).relationshipLevel() >= RelationshipLevel.Friend) {
                 val cityStateBonus = Stats()
+                val eraInfo = civInfo.getEraObject()
 
-                val relevantBonuses =   if (otherCiv.getDiplomacyManager(civInfo.civName).relationshipLevel() == RelationshipLevel.Friend)
+                val relevantBonuses =
-                                            civInfo.getEraObject().friendBonus[otherCiv.cityStateType.name]
+                    when {
-                                        else
+                        eraInfo == null -> null
-                                            civInfo.getEraObject().allyBonus[otherCiv.cityStateType.name]
+                        otherCiv.getDiplomacyManager(civInfo.civName).relationshipLevel() == RelationshipLevel.Friend ->
+                            eraInfo.friendBonus[otherCiv.cityStateType.name]
+                        else -> eraInfo.allyBonus[otherCiv.cityStateType.name]
+                    }
 
                 if (relevantBonuses != null) {
                     for (bonus in relevantBonuses) {
@@ -235,10 +239,15 @@ class CivInfoStats(val civInfo: CivilizationInfo) {
         //From city-states
         for (otherCiv in civInfo.getKnownCivs()) {
             if (otherCiv.isCityState() && otherCiv.getDiplomacyManager(civInfo).relationshipLevel() >= RelationshipLevel.Friend) {
-                val relevantbonuses = if (otherCiv.getDiplomacyManager(civInfo).relationshipLevel() == RelationshipLevel.Friend)
+                val eraInfo = civInfo.getEraObject()
-                                        civInfo.getEraObject().friendBonus[otherCiv.cityStateType.name]
+                val relevantbonuses = 
-                                    else
+                    when {
-                                        civInfo.getEraObject().allyBonus[otherCiv.cityStateType.name]
+                        eraInfo == null -> null
+                        otherCiv.getDiplomacyManager(civInfo).relationshipLevel() == RelationshipLevel.Friend ->
+                            eraInfo.friendBonus[otherCiv.cityStateType.name]
+                        else ->
+                            eraInfo.allyBonus[otherCiv.cityStateType.name]
+                    }
 
                 if (relevantbonuses != null) {
                     for (bonus in relevantbonuses) {

core/src/com/unciv/logic/civilization/CivilizationInfo.kt

@@ -415,7 +415,7 @@ class CivilizationInfo {
 
     fun getEraNumber(): Int = gameInfo.ruleSet.getEraNumber(getEra())
 
-    fun getEraObject(): Era = gameInfo.ruleSet.eras[getEra()]!!
+    fun getEraObject(): Era? = gameInfo.ruleSet.eras[getEra()]
 
     fun isAtWarWith(otherCiv: CivilizationInfo): Boolean {
         if (otherCiv.civName == civName) return false // never at war with itself

core/src/com/unciv/logic/civilization/diplomacy/DiplomacyManager.kt

@@ -510,8 +510,14 @@ class DiplomacyManager() {
             if (relationshipLevel() < RelationshipLevel.Friend) {
                 if (hasFlag(DiplomacyFlags.ProvideMilitaryUnit)) removeFlag(DiplomacyFlags.ProvideMilitaryUnit)
             } else {
-                val relevantBonuses = if (relationshipLevel() == RelationshipLevel.Friend) eraInfo.friendBonus[otherCiv().cityStateType.name]
+                val relevantBonuses =
-                                    else eraInfo.allyBonus[otherCiv().cityStateType.name]
+                    when {
+                        eraInfo == null -> null
+                        relationshipLevel() == RelationshipLevel.Friend ->
+                            eraInfo.friendBonus[otherCiv().cityStateType.name]    
+                        else -> eraInfo.allyBonus[otherCiv().cityStateType.name]
+                    }
+                        
                 if (relevantBonuses == null && otherCiv().cityStateType == CityStateType.Militaristic) {
                     // Deprecated, assume Civ V values for compatibility
                     if (!hasFlag(DiplomacyFlags.ProvideMilitaryUnit) && relationshipLevel() == RelationshipLevel.Friend)

core/src/com/unciv/ui/trade/DiplomacyScreen.kt

@@ -163,24 +163,30 @@ class DiplomacyScreen(val viewingCiv:CivilizationInfo):CameraStageBaseScreen() {
         }
 
         var friendBonusText = "When Friends: ".tr()
-        val friendBonuses = viewingCiv.getEraObject().friendBonus[otherCiv.cityStateType.name]
+        val eraInfo = viewingCiv.getEraObject()
-        if (friendBonuses != null) {
+        val friendBonuses =
-            friendBonusText += friendBonuses.joinToString(separator = ", ") { it.tr() }
+            if (eraInfo == null) null
-        } else {
+            else eraInfo.friendBonus[otherCiv.cityStateType.name]
-            // Deprecated, assume Civ V values for compatibility
+        friendBonusText += 
-            val cultureBonus = if(viewingCiv.getEraNumber() in 0..1) "3" else if (viewingCiv.getEraNumber() in 2..3) "6" else "13"
+            if (friendBonuses != null) {
-            val happinessBonus = if(viewingCiv.getEraNumber() in 0..1) "2" else "3"
+                friendBonuses.joinToString(separator = ", ") { it.tr() }
-            friendBonusText += when (otherCiv.cityStateType) {
+            } else {
-                CityStateType.Militaristic -> "Provides military units every [20] turns".tr()
+                // Deprecated, assume Civ V values for compatibility
-                CityStateType.Cultured -> ("Provides [" + cultureBonus + "] [Culture] per turn").tr()
+                val cultureBonus = if(viewingCiv.getEraNumber() in 0..1) "3" else if (viewingCiv.getEraNumber() in 2..3) "6" else "13"
-                CityStateType.Mercantile -> ("Provides [" + happinessBonus + "] Happiness").tr()
+                val happinessBonus = if(viewingCiv.getEraNumber() in 0..1) "2" else "3"
-                CityStateType.Maritime -> "Provides [2] [Food] [in capital]".tr()
+                when (otherCiv.cityStateType) {
+                    CityStateType.Militaristic -> "Provides military units every [20] turns".tr()
+                    CityStateType.Cultured -> ("Provides [" + cultureBonus + "] [Culture] per turn").tr()
+                    CityStateType.Mercantile -> ("Provides [" + happinessBonus + "] Happiness").tr()
+                    CityStateType.Maritime -> "Provides [2] [Food] [in capital]".tr()
+                }
             }
-        }
 
 
         var allyBonusText = "When Allies: "
-        val allyBonuses = viewingCiv.getEraObject().allyBonus[otherCiv.cityStateType.name]
+        val allyBonuses = 
+            if (eraInfo == null) null
+            else eraInfo.allyBonus[otherCiv.cityStateType.name]
         if (allyBonuses != null) {
             allyBonusText += allyBonuses.joinToString(separator = ", ") { it.tr() }
         } else {