Handle missing nickname in contact details

src/partials/messenger.receiver/contact.html

@@ -29,7 +29,8 @@
 				<dd>{{ ctrl.fingerPrint }}</dd>
 
 				<dt><span translate>messenger.NICKNAME</span></dt>
-				<dd ng-bind-html="ctrl.receiver.publicNickname | emojify"></dd>
+				<dd ng-if="ctrl.receiver.publicNickname" ng-bind-html="ctrl.receiver.publicNickname | emojify"></dd>
+				<dd ng-if="!ctrl.receiver.publicNickname">-</dd>
 
 				<dt><span translate>messenger.FIRST_NAME</span></dt>
 				<dd>{{ ctrl.receiver.firstName || "-" }}</dd>