ui: catch silent EGL failure (#28169)

Co-authored-by: Comma Device <device@comma.ai>

selfdrive/ui/qt/qt_window.cc

@@ -19,6 +19,10 @@ void setMainWindow(QWidget *w) {
   wl_surface_set_buffer_transform(s, WL_OUTPUT_TRANSFORM_270);
   wl_surface_commit(s);
   w->showFullScreen();
+
+  // ensure we have a valid eglDisplay, otherwise the ui will silently fail
+  void *egl = native->nativeResourceForWindow("egldisplay", w->windowHandle());
+  assert(egl != nullptr);
 #endif
 }