Fallback to English and then the key for I18nProvider#t

ui/app/i18n-provider.js

@@ -8,8 +8,11 @@ const t = require('../i18n-helper').getMessage
 class I18nProvider extends Component {
   getChildContext () {
     const { localeMessages } = this.props
+    const { current, en } = localeMessages
     return {
-      t: t.bind(null, localeMessages),
+      t (key, ...args) {
+        return t(current, key, ...args) || t(en, key, ...args) || `[${key}]`
+      },
     }
   }
 

ui/i18n-helper.js

@@ -1,20 +1,22 @@
 // cross-browser connection to extension i18n API
 const log = require('loglevel')
 
+/**
+ * Returns a localized message for the given key
+ * @param {object} locale The locale
+ * @param {string} key The message key
+ * @param {string[]} substitutions A list of message substitution replacements
+ * @return {null|string} The localized message
+ */
 const getMessage = (locale, key, substitutions) => {
-  // check locale is loaded
   if (!locale) {
-    // throw new Error('Translator - has not loaded a locale yet.')
-    return ''
+    return null
   }
-  // check entry is present
-  const { current, en } = locale
-  const entry = current[key] || en[key]
-  if (!entry) {
-    // throw new Error(`Translator - Unable to find value for "${key}"`)
-    log.error(`Translator - Unable to find value for "${key}"`)
-    return `[${key}]`
+  if (!locale[key]) {
+    log.error(`Translator - Unable to find value for key "${key}"`)
+    return null
   }
+  const entry = locale[key]
   let phrase = entry.message
   // perform substitutions
   if (substitutions && substitutions.length) {