Color avatars of non-existing users gray and display X instead

core/js/jquery.avatar.js

@@ -85,7 +85,9 @@
 					if (result.data && result.data.displayname) {
 						$div.imageplaceholder(user, result.data.displayname);
 					} else {
-						$div.imageplaceholder(user);
+						// User does not exist
+						$div.imageplaceholder(user, 'X');
+						$div.css('background-color', '#b9b9b9');
 					}
 				} else {
 					$div.hide();