Merge pull request #4570 from kdmcser/crash_fix

fix Ballista Bank Mod auto combat crash

AI/BattleAI/BattleExchangeVariant.cpp

@@ -296,7 +296,7 @@ ReachabilityInfo getReachabilityWithEnemyBypass(
 				continue;
 
 			auto dmg = damageCache.getOriginalDamage(activeStack, unit, state);
-			auto turnsToKill = unit->getAvailableHealth() / dmg;
+			auto turnsToKill = unit->getAvailableHealth() / std::max(dmg, (int64_t)1);
 
 			vstd::amin(turnsToKill, 100);