Cancel Ajax call when there are only duplicated issues

Also prevent error when issues are not present in the action's params.

Fixes #8872

src/api/app/assets/javascripts/webui/patchinfo.js

@@ -14,10 +14,6 @@ function addIssuesAjaxBefore() {
       return false;
     }
 
-    var element = $(this);
-    element.children('i.fas.fa-plus-circle').addClass('d-none');
-    element.children('i.fas.fa-spin').removeClass('d-none');
-
     issues = $.unique(issues.replace(/ /g, '').split(','));
 
     var currentIssues = $('[name="patchinfo[issueid][]"]').map(function(_, element) {
@@ -33,6 +29,14 @@ function addIssuesAjaxBefore() {
       return currentIssues.indexOf(issue) === -1;
     });
 
+    if (issues.length === 0) {
+      $('#issue_ids').val('');
+      return false;
+    }
+
+    var element = $(this);
+    element.children('i.fas.fa-plus-circle').addClass('d-none');
+    element.children('i.fas.fa-spin').removeClass('d-none');
     element.data('params', { issues: issues, project: element.data('project') });
   });
 }

src/api/app/controllers/webui/patchinfo_controller.rb

@@ -89,6 +89,7 @@ def new_tracker
     error = ''
     invalid_format = ''
     # params[:issues] = list of new issues to add
+    params[:issues] ||= []
     params[:issues].each do |new_issue|
       issue = IssueTracker::IssueTrackerHelper.new(new_issue)
       if issue.valid?