* Add guard exception in OutputPage::parse() for failure case where $wgTitle is null...

* Add guard exception in OutputPage::parse() for failure case where $wgTitle is null; that causes a fatal error which doesn't show a backtrace if we don't catch it here.
* Temporarily set $wgTitle while doing article creation/edit updates during XML import. A null $wgTitle as in importDump.php caused a fatal error when special pages were transcluded if they did any parsing via OutputPage::parse()