Stop QMl JS Debugger connecting if app crashes / hit's C++ breakpoint

For mixed C++/QML debugging, if the app crashes on startup the gdb engine shows the stacktrace etc. However, in the background the Qml engine still tries to connect to the app, and shows the infamous error dialog if it cannot in the given time span.

The Qml Engine should stop trying / pause to connect as soon as the Gdb engine knows the app isn't actually running.