internal: fix minor ubsan errors (#9743)

* opengl: check if g_pHyprOpengl exist

on compositor destruction we can hit a race where a CEGLSync destructs
and tries to call eglDestroySyncKHR on a null g_pHyprOpengl.

/src/render/OpenGL.cpp:3019:32: runtime error: member access within null pointer of type 'struct CHyprOpenGLImpl'
     #0 0x555565eed979 in CEGLSync::~CEGLSync() /src/render/OpenGL.cpp:3019
     #1 0x555565f6271e in std::default_delete<CEGLSync>::operator()(CEGLSync*)
     const /usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/unique_ptr.h:93

* xdgshell: dont apply state on empty states

setsize can be called before a state has been added to pending,
resulting in calling ApplyState with a empty state.

/src/protocols/XDGShell.cpp:323:11: runtime error: null pointer passed as argument 2, which is declared to never be null
     #0 0x5555659bf67e in CXDGToplevelResource::applyState() /src/protocols/XDGShell.cpp:323
     #1 0x5555659bcedc in CXDGToplevelResource::setSize(Hyprutils::Math::Vector2D const&) /src/protocols/XDGShell.cpp:  256
     #2 0x555563eed0ef in Events::listener_commitWindow(void*, void*) /src/events/Windows.cpp:841