DSD Demod crash on exit with high sample rate

[srcejon]

The DSD Demod can crash if it is closed while running with a high sample rate.

To recreate:

• Add test source at 5MS/a and dec=1
• Open DSD Demod
• Run
• Close DSD Demod
• Should crash on Windows and Linux (although not 100% of the time)

0x00007fff6efd0083 in DSDDemodSink::feed(__gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&, __gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&) () from /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
(gdb) info stack
#0 0x00007fff6efd0083 in DSDDemodSink::feed(__gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&, __gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&) () at /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
#1 0x00007ffff7114d3f in DownChannelizer::feed(__gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&, __gnu_cxx::__normal_iterator<Sample const*, std::vector<Sample, std::allocator > > const&) () at /opt/install/sdrangel/lib/sdrangel/libsdrbase.so
#2 0x00007fff6efd4cb4 in DSDDemodBaseband::handleData() () at /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
#3 0x00007fff6efd576a in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, void (DSDDemodBaseband::)()>::call(void (DSDDemodBaseband::)(), DSDDemodBaseband*, void**) () at /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
#4 0x00007fff6efd56ee in void QtPrivate::FunctionPointer<void (DSDDemodBaseband::)()>::call<QtPrivate::List<>, void>(void (DSDDemodBaseband::)(), DSDDemodBaseband*, void**) () at /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
#5 0x00007fff6efd5659 in QtPrivate::QSlotObject<void (DSDDemodBaseband::)(), QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase, QObject*, void**, bool*) () at /opt/install/sdrangel/lib/sdrangel/plugins/libdemoddsd.so
#6 0x00007ffff5ce741e in QObject::event(QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#7 0x00007ffff696c713 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#8 0x00007ffff5cb9e3a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#9 0x00007ffff5cbcf27 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#10 0x00007ffff5d13a67 in () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#11 0x00007ffff4120d3b in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#12 0x00007ffff41756c8 in () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#13 0x00007ffff411e3e3 in g_main_context_iteration () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#14 0x00007ffff5d130b8 in QEventDispatcherGlib::processEvents(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#15 0x00007ffff5cb875b in QEventLoop::exec(QFlagsQEventLoop::ProcessEventsFlag) () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#16 0x00007ffff5acbaf2 in QThread::exec() () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#17 0x00007ffff5accca1 in () at /lib/x86_64-linux-gnu/libQt5Core.so.5
#18 0x00007ffff5294b43 in start_thread (arg=) at ./nptl/pthread_create.c:442
#19 0x00007ffff5326a00 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81