Commands now give useful error messages even without consoleTrace active

[klianc09]

When consoleTrace is set to false, exceptions in commands will lead to useless messages:

Exception occurred in method: failFunction

This is caused by the fact that com.badlogic.gdx.utils.reflect.invoke() wraps the TargetInvokationException with a ReflectionException with that predefined message, therefore the check for an empty message in AbstractConsole is never true in that case.

if (msg == null || msg.length() <= 0) {
  msg = "Unknown Error";
  e.printStackTrace();
}

With this change the example failFunction command in Box2DTest will print the much more helpful:

Exception occurred in method: failFunction
java.lang.RuntimeException: This function was designed to fail.

Only tested on desktop. If it causes issues with GWT, the import might need to be avoided, but so far untested.