Fixes #3950 - Uncaught TypeError in ticket zoom highlighter

app/assets/javascripts/app/controllers/ticket_zoom/highlighter.coffee

@@ -212,6 +212,8 @@ class App.TicketZoomHighlighter extends App.Controller
   # - clears the selection
 
   toggleHighlightAtSelection: (article, article_id) =>
+    return if !article
+
     selection = rangy.getSelection()
 
     # activate selection background

app/assets/javascripts/app/views/layout_ref/ticket_zoom.jst.eco

@@ -12,7 +12,7 @@
           </div>
           <ul class="dropdown-menu dropdown-menu-right" role="menu">
             <% for entry, i in @colors: %>
-            <li role="presentation">
+            <li role="presentation" class="dropdown-highlight-list">
               <a role="menuitem" tabindex="-1" class="js-highlightColor" data-key="<%= i %>">
                 <span class="dropdown-iconSpacer">
                   <span class="color-swatch icon" style="color: <%= entry.color %>"></span>

app/assets/javascripts/app/views/ticket_zoom/highlighter.jst.eco

@@ -7,7 +7,7 @@
   </div>
   <ul class="dropdown-menu dropdown-menu-right" role="menu">
     <% for entry, i in @colors: %>
-    <li role="presentation">
+    <li role="presentation" class="dropdown-highlight-list">
       <a role="menuitem" tabindex="-1" class="js-highlightColor" data-key="<%= i %>">
         <span class="dropdown-iconSpacer">
           <span class="color-swatch icon" style="color: <%= entry.color %>"></span>

app/assets/stylesheets/zammad.scss

@@ -9025,6 +9025,15 @@ a.list-group-item.active > .badge,
     padding: 0 18px;
   }
 
+  li.dropdown-highlight-list {
+    // remove padding to add more click area for anchor tag
+    padding: 0;
+
+    a {
+      padding: 11px 18px;
+    }
+  }
+
   .icon {
     fill: currentColor;
   }