GUAC-1172: Upgrade angular-translate to 2.7.2. Configure required sanitization strategy. Use null instead of false for lack of login error.

guacamole/src/main/webapp/app/index/config/indexTranslationConfig.js

@@ -36,6 +36,9 @@ angular.module('index').config(['$injector', function($injector) {
     $translateProvider.fallbackLanguage(fallbackLanguages);
     $translateProvider.preferredLanguage(preferenceServiceProvider.preferences.language);
 
+    // Escape any HTML in translation strings
+    $translateProvider.useSanitizeValueStrategy('escape');
+
     // Load translations via translationLoader service
     $translateProvider.useLoader('translationLoader', {
         fallbackLanguages : fallbackLanguages