function extendLanguageDictionary(languageCode, dictionary) {
  if (languageCode !== DEFAULT_LANGUAGE_CODE) {
    (0, _utils.extendNotExistingKeys)(dictionary, getGlobalLanguageDictionary(DEFAULT_LANGUAGE_CODE));
  }
}
Extend handled dictionary by default language dictionary. As result, if any dictionary key isn't defined for specific language, it will be filled with default language value ("dictionary gaps" are supplemented).

@private
@param {String} languageCode Language code.
@param {Object} dictionary Dictionary which is extended.