fix return value of dummy_window_get_egl_surface when surface couldn't be created

return EGL_NO_SURFACE if render_surface couldn't be created

Author: ardera

src/window.c

@@ -1751,6 +1751,10 @@ static EGLSurface dummy_window_get_egl_surface(struct window *window) {
 
     if (window->renderer_type == kOpenGL_RendererType) {
         struct render_surface *render_surface = dummy_window_get_render_surface_internal(window, false, VEC2I(0, 0));
+        if (render_surface == NULL) {
+            return EGL_NO_SURFACE;
+        }
+        
         return egl_gbm_render_surface_get_egl_surface(CAST_EGL_GBM_RENDER_SURFACE(render_surface));
     } else {
         return EGL_NO_SURFACE;