Make clients exit orderly when there is no connection
diff --git a/clients/dnd.c b/clients/dnd.c
index 766fc5c..dedf353 100644
--- a/clients/dnd.c
+++ b/clients/dnd.c
@@ -581,6 +581,10 @@
 	srandom(tv.tv_usec);
 
 	d = display_create(&argc, &argv, option_entries);
+	if (d == NULL) {
+		fprintf(stderr, "failed to create display: %m\n");
+		return -1;
+	}
 
 	display_set_drag_offer_handler(d, drag_offer_handler);