Fix error message for existing labels.

CHANGELOG

@@ -112,6 +112,9 @@ v 8.10.3
   - Fix importer for GitHub Pull Requests when a branch was removed. !5573
   - Ignore invalid IPs in X-Forwarded-For when trusted proxies are configured. !5584
   - Trim extra displayed carriage returns in diffs and files with CRLFs. !5588
+  - Fix label already exist error message in the right sidebar.
+
+v 8.10.3 (unreleased)
 
 v 8.10.2
   - User can now search branches by name. !5144

app/assets/javascripts/labels_select.js

@@ -70,13 +70,15 @@
               name: newLabelField.val(),
               color: newColorField.val()
             }, function(label) {
-              var errors;
               $newLabelCreateButton.enable();
               if (label.message != null) {
-                errors = _.map(label.message, function(value, key) {
-                  return key + " " + value[0];
-                });
-                return $newLabelError.html(errors.join("<br/>")).show();
+                var errorText = label.message;
+                if (_.isObject(label.message)) {
+                  errorText = _.map(label.message, function(value, key) {
+                    return key + " " + value[0];
+                  }).join('<br/>');
+                }
+                return $newLabelError.html(errorText).show();
               } else {
                 return $('.dropdown-menu-back', $dropdown.parent()).trigger('click');
               }