Put default theme/language in URL cache, when none specified in url

In-Portal parses each url on a front-end (when mod-rewrite is enabled) into a set of variables and stores them into cache.

However, when In-Portal encounters and url without theme/language specified (e.g. /english.html or /advanced.html) it:

• produces a warning, that m_lang or m_theme variable is undefined
• parsed url is cached without language/theme id specified resulting such cache not reset automatically on language/theme data change.