Render screen on window restored

It should not be necessary, since screen_render() is called just after
on SDL_WINDOWEVENT_EXPOSED, but in practice the window content might not
be correctly displayed on restored if a rotation occurred while
minimized.

Note that calling screen_render() twice in a row on
SDL_WINDOWEVENT_EXPOSED also "fixes" the issue.

app/src/screen.c

@@ -726,6 +726,7 @@ screen_handle_event(struct screen *screen, SDL_Event *event) {
                     }
                     screen->maximized = false;
                     apply_pending_resize(screen);
+                    screen_render(screen, true);
                     break;
             }
             return true;