Fix #4585

Author: CasualPokePlayer

ExternalProjects/NLua/src/ObjectTranslator.cs

@@ -880,6 +880,11 @@ internal LuaTable GetTable(LuaState luaState, int index)
 			// Before create new tables, check if there is any finalized object to clean.
 			CleanFinalizedReferences(luaState);
 
+			if (luaState.Type(index) != LuaType.Table)
+			{
+				return null;
+			}
+
 			luaState.PushCopy(index);
 			var reference = luaState.Ref(LuaRegistry.Index);
 			return reference == -1 ? null : new LuaTable(reference, interpreter);
@@ -893,6 +898,11 @@ internal LuaThread GetThread(LuaState luaState, int index)
 			// Before create new tables, check if there is any finalized object to clean.
 			CleanFinalizedReferences(luaState);
 
+			if (luaState.Type(index) != LuaType.Thread)
+			{
+				return null;
+			}
+
 			luaState.PushCopy(index);
 			var reference = luaState.Ref(LuaRegistry.Index);
 			return reference == -1 ? null : new LuaThread(reference, interpreter);
@@ -906,6 +916,11 @@ internal LuaUserData GetUserData(LuaState luaState, int index)
 			// Before create new tables, check if there is any finalized object to clean.
 			CleanFinalizedReferences(luaState);
 
+			if (luaState.Type(index) != LuaType.UserData)
+			{
+				return null;
+			}
+
 			luaState.PushCopy(index);
 			var reference = luaState.Ref(LuaRegistry.Index);
 			return reference == -1 ? null : new LuaUserData(reference, interpreter);
@@ -919,6 +934,11 @@ internal LuaFunction GetFunction(LuaState luaState, int index)
 			// Before create new tables, check if there is any finalized object to clean.
 			CleanFinalizedReferences(luaState);
 
+			if (luaState.Type(index) != LuaType.Function)
+			{
+				return null;
+			}
+
 			luaState.PushCopy(index);
 			var reference = luaState.Ref(LuaRegistry.Index);
 			return reference == -1 ? null : new LuaFunction(reference, interpreter);