Destruction of QOSCServer with PathObjects registered triggers access violation

[timmb]

QOSCServer triggers a crash when it is destroyed with path objects registered. This is because the child path objects are destroyed by QOSCServer's base QObject desctructor which causes them to unregister from OSC Server but this happens after QOSCServer's destructor so the paths member of QOSCServer has already been destroyed.

Will submit a pull request.