Hotfix errorhandler

SpigotCore_Main/src/de/steamwar/core/ErrorHandler.java

@@ -70,6 +70,7 @@ public class ErrorHandler extends Handler {
         }
 
         ByteArrayOutputStream stacktraceOutput = new ByteArrayOutputStream();
+        if(logRecord.getThrown() != null)
             logRecord.getThrown().printStackTrace(new PrintStream(stacktraceOutput));
         String stacktrace = stacktraceOutput.toString();
         if(stacktrace.contains("POI data mismatch"))