Don't insert mention when clicking non-privmsg

This goes in the direction of #860 but actually removing the tag seems
to be rather more involved

index.html

@@ -334,7 +334,7 @@ npm run build-electron-{windows, darwin, linux}</pre>
                   <span class="cof-chat_time cob-chat_time coa-chat_time" ng-bind-html="::bufferline.formattedTime"></span>
                 </span>
               </td>
-              <td class="prefix"><span ng-class="::{'repeated-prefix': bufferline.prefixtext==bufferlines[$index-1].prefixtext}"><a ng-click="addMention(bufferline.prefix)"><span class="hidden-bracket" ng-if="::(bufferline.showHiddenBrackets)">&lt;</span><span ng-repeat="part in ::bufferline.prefix" ng-class="::part.classes" ng-bind="::part.text|prefixlimit:25"></span><span class="hidden-bracket" ng-if="::(bufferline.showHiddenBrackets)">&gt;</span></a></span></td><!--
+              <td class="prefix"><span ng-class="::{'repeated-prefix': bufferline.prefixtext==bufferlines[$index-1].prefixtext}"><a ng-click="addMention(bufferline)"><span class="hidden-bracket" ng-if="::(bufferline.showHiddenBrackets)">&lt;</span><span ng-repeat="part in ::bufferline.prefix" ng-class="::part.classes" ng-bind="::part.text|prefixlimit:25"></span><span class="hidden-bracket" ng-if="::(bufferline.showHiddenBrackets)">&gt;</span></a></span></td><!--
            --><td class="message"><!--
              --><div ng-repeat="metadata in ::bufferline.metadata" plugin data="::metadata"></div><!--
              --><span ng-repeat="part in ::bufferline.content" class="text" ng-class="::part.classes.concat(['line-' + part.$$hashKey.replace(':','_')])" ng-bind-html="::part.text | linky:'_blank':{rel:'noopener noreferrer'} | DOMfilter:'irclinky' | DOMfilter:'emojify':settings.enableJSEmoji | DOMfilter:'inlinecolour' | DOMfilter:'latexmath':('.line-' + part.$$hashKey.replace(':','_')):settings.enableMathjax"></span>

js/inputbar.js

@@ -208,7 +208,12 @@ weechat.directive('inputBar', function() {
             };
 
             //XXX THIS DOES NOT BELONG HERE!
-            $rootScope.addMention = function(prefix) {
+            $rootScope.addMention = function(bufferline) {
+                if (!bufferline.showHiddenBrackets) {
+                    // the line is a notice or action or something else that doesn't belong
+                    return;
+                }
+                var prefix = bufferline.prefix;
                 // Extract nick from bufferline prefix
                 var nick = prefix[prefix.length - 1].text;