[1.9.x] Fixed #26046 -- Fixed a crash with translations and Django-unknown language code

Thanks Jens Lundstrom for the report and Tim Graham for the review.
Backport of 632a9f21bc from master.

django/utils/translation/trans_real.py

@@ -117,6 +117,9 @@ class DjangoTranslation(gettext_module.GNUTranslations):
             # default lang should have at least one translation file available.
             raise IOError("No translation files found for default language %s." % settings.LANGUAGE_CODE)
         self._add_fallback()
+        if self._catalog is None:
+            # No catalogs found for this language, set an empty catalog.
+            self._catalog = {}
 
     def __repr__(self):
         return "<DjangoTranslation lang:%s>" % self.__language

docs/releases/1.8.9.txt

@@ -11,3 +11,6 @@ Bugfixes
 
 * Fixed a regression that caused the "user-tools" items to display on the
   admin's logout page (:ticket:`26035`).
+
+* Fixed a crash in the translations system when the current language has no
+  translations (:ticket:`26046`).

docs/releases/1.9.2.txt

@@ -9,8 +9,11 @@ Django 1.9.2 fixes several bugs in 1.9.1.
 Bugfixes
 ========
 
-* Fixed a regression in ``ConditionalGetMiddleware`` causing ``If-None-Match`` checks
-  to always return HTTP 200 (:ticket:`26024`).
+* Fixed a regression in ``ConditionalGetMiddleware`` causing ``If-None-Match``
+  checks to always return HTTP 200 (:ticket:`26024`).
 
 * Fixed a regression that caused the "user-tools" items to display on the
   admin's logout page (:ticket:`26035`).
+
+* Fixed a crash in the translations system when the current language has no
+  translations (:ticket:`26046`).

tests/i18n/tests.py

@@ -1577,6 +1577,10 @@ class TestLanguageInfo(SimpleTestCase):
 
     def test_unknown_language_code(self):
         six.assertRaisesRegex(self, KeyError, r"Unknown language code xx\.", get_language_info, 'xx')
+        with translation.override('xx'):
+            # A language with no translation catalogs should fallback to the
+            # untranslated string.
+            self.assertEqual(ugettext("Title"), "Title")
 
     def test_unknown_only_country_code(self):
         li = get_language_info('de-xx')