Check for surface vilidaty before destrying

Author: EddyGharbi

src/window-osx.mm

@@ -398,6 +398,9 @@ @implementation WindowImplObj
     return;
 
   WindowInfo* wi = reinterpret_cast<WindowInfo*>(it->second);
+  if (!wi->view.glData->surface)
+    return;
+
   wi->view.glData->mtx.lock();
   wi->view.glData->stop = true;