Hotfix SimulatorStorage

BauSystem_Main/src/de/steamwar/bausystem/features/simulator/SimulatorStorage.java

@@ -84,7 +84,9 @@ public class SimulatorStorage implements Enable {
         SimulatorFormatSimulatorLoader simulatorFormatSimulatorLoader = new SimulatorFormatSimulatorLoader();
         YAPIONFormatSimulatorLoader yapionFormatSimulatorLoader = new YAPIONFormatSimulatorLoader();
 
-        for (File file : simulatorsDir.listFiles()) {
+        File[] files = simulatorsDir.listFiles();
+        if (files == null) return;
+        for (File file : files) {
             try {
                 List<Simulator> simulators = simFormatSimulatorLoader.load(file)
                         .orElse(null);