Checks for relatedTarget

If related target is undefined then we can't complete the below code

app/assets/javascripts/gl_dropdown.js.coffee

@@ -217,11 +217,12 @@ class GitLabDropdown
       if e.which is 27 # Escape key
         $('.dropdown-menu-close', @dropdown).trigger 'click'
     @dropdown.on 'blur', 'a', (e) =>
-      $relatedTarget = $(e.relatedTarget)
-      $dropdownMenu = $relatedTarget.closest('.dropdown-menu')
-      if $dropdownMenu.length is 0
-        @dropdown.removeClass('open')
+      if e.relatedTarget?
+        $relatedTarget = $(e.relatedTarget)
+        $dropdownMenu = $relatedTarget.closest('.dropdown-menu')
+        if $dropdownMenu.length is 0
+          @dropdown.removeClass('open')
     if @dropdown.find(".dropdown-toggle-page").length
       @dropdown.find(".dropdown-toggle-page, .dropdown-menu-back").on "click", (e) =>