Crash when closing GUI

[dwuertz]

Test Evnironment: Linux / REAPER 6.24 / VST3
sfizz: d2b9eb7

#0 0x00007ffff79c9ef5 in raise () at /usr/lib/libc.so.6
sfztools/sfizz#1 0x00007ffff79b3862 in abort () at /usr/lib/libc.so.6
sfztools/sfizz#2 0x00007ffff7a0bf38 in __libc_message () at /usr/lib/libc.so.6
sfztools/sfizz#3 0x00007ffff7a13bea in () at /usr/lib/libc.so.6
sfztools/sfizz#4 0x00007ffff7a1547c in _int_free () at /usr/lib/libc.so.6
sfztools/sfizz#5 0x00007ffff7a18ca8 in free () at /usr/lib/libc.so.6
sfztools/sfizz#6 0x00007fffca0f004e in SPiano::~SPiano() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-linux/sfizz.so
sfztools/sfizz#7 0x00007fffca15e985 in VSTGUI::CViewContainer::removeAll(bool) () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-lin
ux/sfizz.so
sfztools/sfizz#8 0x00007fffca15ec2b in VSTGUI::CViewContainer::beforeDelete() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-linu
x/sfizz.so
sfztools/sfizz#9 0x00007fffca0b4f3f in VSTGUI::ReferenceCounted::forget() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-lin
ux/sfizz.so
sfztools/sfizz#10 0x00007fffca0e4235 in Editor::Impl::~Impl() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-linux/sfizz.so
sfztools/sfizz#11 0x00007fffca0b79c5 in SfizzVstEditor::~SfizzVstEditor() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-linux/sfi
zz.so
sfztools/sfizz#12 0x00007fffca0b7b69 in SfizzVstEditor::~SfizzVstEditor() () at /home/dude/.vst3/sfizz.vst3/Contents/x86_64-linux/sfi
zz.so
sfztools/sfizz#13 0x00007fffca0adc25 in non-virtual thunk to Steinberg::Vst::VSTGUIEditor::release() () at /home/dude/.vst3/sfizz.vst

[dwuertz]

new Core dump with Debug build:
#0 0x00007ffff79c9ef5 in raise () at /usr/lib/libc.so.6
sfztools/sfizz#1 0x00007ffff79b3862 in abort () at /usr/lib/libc.so.6
sfztools/sfizz#2 0x00007ffff7a0bf38 in __libc_message () at /usr/lib/libc.so.6
sfztools/sfizz#3 0x00007ffff7a13bea in () at /usr/lib/libc.so.6
sfztools/sfizz#4 0x00007ffff7a14fbc in _int_free () at /usr/lib/libc.so.6
sfztools/sfizz#5 0x00007ffff7a18ca8 in free () at /usr/lib/libc.so.6
sfztools/sfizz#6 0x00007ffff6a9df3e in xkb_keymap_unref () at /usr/lib/libxkbcommon.so.0
sfztools/sfizz#7 0x00007fffc9f75b7f in VSTGUI::X11::RunLoop::Impl::exit() (this=0x1335760) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/platform/linux/x11platform.cpp:218
sfztools/sfizz#8 0x00007fffc9f74d17 in VSTGUI::X11::RunLoop::exit() () at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/platform/linux/x11platform.cpp:419
sfztools/sfizz#9 0x00007fffc9f6f424 in VSTGUI::X11::Frame::~Frame() (this=0x22f61a0, __in_chrg=, __vtt_parm=) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/platform/linux/x11frame.cpp:591
sfztools/sfizz#10 0x00007fffc9f6f47e in VSTGUI::X11::Frame::~Frame() (this=0x22f61a0, __in_chrg=, __vtt_parm=) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/platform/linux/x11frame.cpp:592
sfztools/sfizz#11 0x00007fffc9e21ad8 in VSTGUI::ReferenceCounted<std::atomic >::forget() (this=0x22f61a0) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/vstguibase.h:280
sfztools/sfizz#12 0x00007fffc9ef9499 in VSTGUI::SharedPointerVSTGUI::IPlatformFrame::operator=(VSTGUI::IPlatformFrame*) (this=0x1d31f70, _ptr=0x0) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/vstguibase.h:447
sfztools/sfizz#13 0x00007fffc9eeff73 in VSTGUI::CFrame::close() (this=0x10fb1a0) at /home/dude/sources/sfizz/plugins/editor/external/vstgui4/vstgui/lib/cframe.cpp:195
sfztools/sfizz#14 0x00007fffc9e1d763 in SfizzVstEditor::close() (this=0x1b71660) at /home/dude/sources/sfizz/plugins/vst/SfizzVstEditor.cpp:122
sfztools/sfizz#15 0x00007fffc9e80a80 in Steinberg::Vst::VSTGUIEditor::removed() (this=0x1b71660) at /home/dude/sources/sfizz/plugins/vst/external/VST_SDK/VST3_SDK/public.sdk/source/vst/vstguieditor.cpp:191

[jpcima]

We have an anomaly at vstgui x11timer.cpp.
In the function Timer::stop, there is an early return without unregistering the timer, if the condition runLoop=null.
Due to not unregistering the timer, it continues to get triggered shortly after and causes the crash.
It needs to check what exactly happens with the runloop.