clients/simple-egl: Exit when display has an error

Check return values for wl_display_dispatch_* functions, so that
the program stops running when the compositor that it is connected
to crashes.

Signed-off-by: Manuel Stoeckl <code@mstoeckl.com>

clients/simple-egl.c

@@ -866,9 +866,9 @@ main(int argc, char **argv)
 	 * queued up as a side effect. */
 	while (running && ret != -1) {
 		if (window.wait_for_configure) {
-			wl_display_dispatch(display.display);
+			ret = wl_display_dispatch(display.display);
 		} else {
-			wl_display_dispatch_pending(display.display);
+			ret = wl_display_dispatch_pending(display.display);
 			redraw(&window, NULL, 0);
 		}
 	}