Pass DefaultScreen(display) to glXQueryExtensions

Pass DefaultScreen(display) as the screen number to
glXQueryExtensionsString(display, screen), this may work more reliably
for some configurations than always assuming screen 0.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

src/wx/panel.cpp

@@ -2170,7 +2170,9 @@ void GLDrawingPanel::DrawingPanelInit()
     static PFNGLXSWAPINTERVALSGIPROC glXSwapIntervalSGI = NULL;
     static PFNGLXSWAPINTERVALMESAPROC glXSwapIntervalMESA = NULL;
 
-    char* glxQuery = (char*)glXQueryExtensionsString(glXGetCurrentDisplay(), 0);
+    auto display = glXGetCurrentDisplay();
+
+    char* glxQuery = (char*)glXQueryExtensionsString(display, DefaultScreen(display));
 
     if (strstr(glxQuery, "GLX_EXT_swap_control") != NULL)
     {