Fix empty default lang bug (commons-app#4608)

* Fix bug commons-app#4583

* Fix empty default lang bug

Author: madhurgupta10

app/src/main/java/fr/free/nrw/commons/settings/SettingsFragment.java

@@ -229,7 +229,10 @@ private void prepareAppLanguages(final String keyListPreference) {
     /**
      * Changing the default app language with selected one and save it to SharedPreferences
      */
-    public void setLocale(final Activity activity, final String userSelectedValue) {
+    public void setLocale(final Activity activity, String userSelectedValue) {
+        if (userSelectedValue.equals("")) {
+            userSelectedValue = Locale.getDefault().getLanguage();
+        }
         final Locale locale = new Locale(userSelectedValue);
         Locale.setDefault(locale);
         final Configuration configuration = new Configuration();