Fix navigation header

Apparently in newer versions of ng-material or angularjs, the "ng-click"
attribute may not be an empty string.

src/partials/messenger.navigation.html

@@ -45,10 +45,10 @@
 <div id="navigation-header">
     <div class="main">
         <md-nav-bar md-no-ink md-selected-nav-item="ctrl.activeTab" nav-bar-aria-label="navigation links">
-            <md-nav-item md-nav-click="" name="conversations">
+            <md-nav-item md-nav-click="1" name="conversations">
                 <i class="material-icons md-dark md-24" translate translate-attr-title="messenger.CONVERSATIONS">speaker_notes</i>
             </md-nav-item>
-            <md-nav-item md-nav-click="" name="contacts">
+            <md-nav-item md-nav-click="1" name="contacts">
                 <i class="material-icons md-dark md-24" translate translate-attr-title="messenger.CONTACTS">person</i>
             </md-nav-item>
         </md-nav-bar>