window: check the initial wl_display_dispatch()

Check for errors in the first wl_display_dispatch() call. Otherwise
doing something silly like
  $ WAYLAND_SOCKET=999 ./clickdot
will segfault.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

clients/window.c

@@ -4287,7 +4287,12 @@ display_create(int argc, char *argv[])
 
 	d->registry = wl_display_get_registry(d->display);
 	wl_registry_add_listener(d->registry, &registry_listener, d);
-	wl_display_dispatch(d->display);
+
+	if (wl_display_dispatch(d->display) < 0) {
+		fprintf(stderr, "Failed to process Wayland connection: %m\n");
+		return NULL;
+	}
+
 #ifdef HAVE_CAIRO_EGL
 	if (init_egl(d) < 0)
 		fprintf(stderr, "EGL does not seem to work, "