Bug 1002534- Password change disambiguation dialog can show <> as a username r=MattN

Differential Revision: https://phabricator.services.mozilla.com/D18749

--HG--
extra : moz-landing-system : lando

toolkit/components/passwordmgr/nsLoginManagerPrompter.js

@@ -1209,7 +1209,7 @@ LoginManagerPrompter.prototype = {
   promptToChangePasswordWithUsernames(logins, count, aNewLogin) {
     this.log("promptToChangePasswordWithUsernames with count:", count);
 
-    var usernames = logins.map(l => l.username);
+    var usernames = logins.map(l => l.username || this._getLocalizedString("noUsername"));
     var dialogText  = this._getLocalizedString("userSelectText2");
     var dialogTitle = this._getLocalizedString("passwordChangeTitle");
     var selectedIndex = { value: null };