Adding TX RemoteOutput device crashes

[srcejon]

Adding a TX RemoteOuput device causes a crash on Linux and Windows.

(I wasn't actually trying to use it, just noticed it while testing something else)

0x00007ffff72ca688 in DeviceSampleSink::getMessageQueueToGUI() () from /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
(gdb) info stack
#0 0x00007ffff72ca688 in DeviceSampleSink::getMessageQueueToGUI() () at /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
#1 0x00007ffff72cd661 in DSPDeviceSinkEngine::handleInputMessages() () at /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
#2 0x00007ffff727e345 in DSPDeviceSinkEngine::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () at /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
#3 0x00007ffff615a41e in QObject::event(QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#4 0x00007ffff6c1e713 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#5 0x00007ffff612ce3a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#6 0x00007ffff612ff27 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#7 0x00007ffff6186a67 in () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#8 0x00007ffff4492d1b in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#9 0x00007ffff44e76f8 in () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#10 0x00007ffff44903c3 in g_main_context_iteration () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#11 0x00007ffff61860b8 in QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#12 0x00007ffff612b75b in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x00007ffff5f3eaf2 in QThread::exec() () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#14 0x00007ffff72ca84f in DSPDeviceSinkEngine::run() () at /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
#15 0x00007ffff5f3fca1 in () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#16 0x00007ffff5a95b43 in start_thread (arg=) at ./nptl/pthread_create.c:442
#17 0x00007ffff5b27a00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81