Mods can handle situations where there is no military unit that is available for construction

core/src/com/unciv/logic/automation/Automation.kt

@@ -20,29 +20,25 @@ object Automation {
 
     private fun rankStatsForCityWork(stats: Stats, city: CityInfo, foodWeight: Float = 1f): Float {
         var rank = 0f
-        if(city.population.population < 5){
+        if (city.population.population < 5) {
             // "small city" - we care more about food and less about global problems like gold science and culture
             rank += stats.food * 1.2f * foodWeight
             rank += stats.production
-            rank += stats.science/2
+            rank += stats.science / 2
-            rank += stats.culture/2
+            rank += stats.culture / 2
             rank += stats.gold / 5 // it's barely worth anything at this points
-        }
+        } else {
-        else{
+            if (stats.food <= 2 || city.civInfo.getHappiness() > 5) rank += stats.food * 1.2f * foodWeight //food get more value to keep city growing
-            if (stats.food <= 2 || city.civInfo.getHappiness() > 5) rank += (stats.food * 1.2f * foodWeight) //food get more value to keep city growing
+            else rank += (2.4f + (stats.food - 2) / 2) * foodWeight // 1.2 point for each food up to 2, from there on half a point
-            else rank += ((2.4f + (stats.food - 2) / 2) * foodWeight) // 1.2 point for each food up to 2, from there on half a point
 
             if (city.civInfo.gold < 0 && city.civInfo.statsForNextTurn.gold <= 0) rank += stats.gold // we have a global problem
             else rank += stats.gold / 3 // 3 gold is worse than 2 production
 
             rank += stats.production
             rank += stats.science
-            if (city.tiles.size < 12 || city.civInfo.victoryType() == VictoryType.Cultural){
+            if (city.tiles.size < 12 || city.civInfo.victoryType() == VictoryType.Cultural) {
                 rank += stats.culture
-            }
+            } else rank += stats.culture / 2
-            else{
-                rank += stats.culture / 2
-            }
         }
         return rank
     }
@@ -53,19 +49,20 @@ object Automation {
         return rank
     }
 
-    fun trainMilitaryUnit(city: CityInfo) {
+    fun tryTrainMilitaryUnit(city: CityInfo) {
-        val name = chooseMilitaryUnit(city)
+        val chosenUnitName = chooseMilitaryUnit(city)
-        city.cityConstructions.currentConstructionFromQueue = name
+        if (chosenUnitName != null)
+            city.cityConstructions.currentConstructionFromQueue = chosenUnitName
     }
 
-    fun chooseMilitaryUnit(city: CityInfo) : String {
+    fun chooseMilitaryUnit(city: CityInfo) : String? {
         var militaryUnits = city.cityConstructions.getConstructableUnits().filter { !it.unitType.isCivilian() }
         if (militaryUnits.map { it.name }.contains(city.cityConstructions.currentConstructionFromQueue))
             return city.cityConstructions.currentConstructionFromQueue
 
         // This is so that the AI doesn't use all its aluminum on units and have none left for spaceship parts
         val aluminum = city.civInfo.getCivResourcesByName()["Aluminum"]
-        if (aluminum!=null && aluminum < 2) // mods may have no aluminum
+        if (aluminum != null && aluminum < 2) // mods may have no aluminum
             militaryUnits.filter { it.requiredResource != "Aluminum" }
 
         val findWaterConnectedCitiesAndEnemies = BFS(city.getCenterTile()) { it.isWater || it.isCityCenter() }
@@ -81,8 +78,9 @@ object Automation {
                 && militaryUnits.any { it.unitType == UnitType.Ranged }) // this is for city defence so get an archery unit if we can
             chosenUnit = militaryUnits.filter { it.unitType == UnitType.Ranged }.maxBy { it.cost }!!
         else { // randomize type of unit and take the most expensive of its kind
-            val chosenUnitType = militaryUnits.map { it.unitType }.distinct().filterNot { it == UnitType.Scout }.toList().random()
+            val availableTypes = militaryUnits.map { it.unitType }.distinct().filterNot { it == UnitType.Scout }.toList()
-            chosenUnit = militaryUnits.filter { it.unitType == chosenUnitType }.maxBy { it.cost }!!
+            if (availableTypes.isEmpty()) return null
+            chosenUnit = militaryUnits.filter { it.unitType == availableTypes.random() }.maxBy { it.cost }!!
         }
         return chosenUnit.name
     }

core/src/com/unciv/logic/automation/ConstructionAutomation.kt

@@ -96,10 +96,11 @@ class ConstructionAutomation(val cityConstructions: CityConstructions){
     }
 
     private fun addMilitaryUnitChoice() {
-        if(!isAtWar && !cityIsOverAverageProduction) return // don't make any military units here. Infrastructure first!
+        if (!isAtWar && !cityIsOverAverageProduction) return // don't make any military units here. Infrastructure first!
         if ((!isAtWar && civInfo.statsForNextTurn.gold > 0 && militaryUnits < cities * 2)
                 || (isAtWar && civInfo.gold > -50)) {
             val militaryUnit = Automation.chooseMilitaryUnit(cityInfo)
+            if (militaryUnit == null) return
             val unitsToCitiesRatio = cities.toFloat() / (militaryUnits + 1)
             // most buildings and civ units contribute the the civ's growth, military units are anti-growth
             var modifier = sqrt(unitsToCitiesRatio) / 2
@@ -107,7 +108,7 @@ class ConstructionAutomation(val cityConstructions: CityConstructions){
             else if (isAtWar) modifier *= unitsToCitiesRatio * 2
             if (!cityIsOverAverageProduction) modifier /= 5 // higher production cities will deal with this
 
-            val civilianUnit = cityInfo.getCenterTile().civilianUnit 
+            val civilianUnit = cityInfo.getCenterTile().civilianUnit
             if (civilianUnit != null && civilianUnit.hasUnique(Constants.settlerUnique)
                     && cityInfo.getCenterTile().getTilesInDistance(5).none { it.militaryUnit?.civInfo == civInfo })
                 modifier = 5f // there's a settler just sitting here, doing nothing - BAD

core/src/com/unciv/logic/automation/NextTurnAutomation.kt

@@ -11,7 +11,6 @@ import com.unciv.logic.civilization.diplomacy.RelationshipLevel
 import com.unciv.logic.map.BFS
 import com.unciv.logic.map.MapUnit
 import com.unciv.logic.trade.*
-import com.unciv.models.ruleset.ModOptions
 import com.unciv.models.ruleset.ModOptionsConstants
 import com.unciv.models.ruleset.VictoryType
 import com.unciv.models.ruleset.tech.Technology
@@ -473,7 +472,7 @@ object NextTurnAutomation{
 
             city.cityConstructions.chooseNextConstruction()
             if (city.health < city.getMaxHealth())
-                Automation.trainMilitaryUnit(city) // override previous decision if city is under attack
+                Automation.tryTrainMilitaryUnit(city) // override previous decision if city is under attack
         }
     }