vo_opengl: initialize renderer after setting size

This silences the warning:

video/out/gl_video.c:1091:51: runtime error: division by zero

when running with clang -fsanitize=undefined. Division by zero is legal
according to IEEE, but I guess clang doesn't care about standard. While
triggering this warning isn't actually avoided in all cases, it's
avoided in the common case and also makes people shut up about it.

video/out/gl_video.c

@@ -2324,6 +2324,8 @@ void gl_video_config(struct gl_video *p, struct mp_image_params *params)
         uninit_video(p);
         init_video(p, params);
     }
+
+    check_resize(p);
 }
 
 void gl_video_set_output_depth(struct gl_video *p, int r, int g, int b)

video/out/vo_opengl.c

@@ -225,12 +225,12 @@ static int reconfig(struct vo *vo, struct mp_image_params *params, int flags)
         p->glctx->register_resize_callback(vo, video_resize_redraw_callback);
     }
 
+    resize(p);
+
     gl_video_config(p->renderer, params);
 
     p->vo_flipped = !!(flags & VOFLAG_FLIPPING);
 
-    resize(p);
-
     mpgl_unlock(p->glctx);
 
     return 0;