Adding additional check for blank language

Addresses #2366
Set lang to 'en' if it happens to be blank.

As a last-ditch fallback. Addresses #2366.
Fixing issue with RSS page header
Changed the robots index, follow columns to null by default
Merge branch '2.2/master' of git://github.com/pyrocms/pyrocms into develop

Conflicts:
	system/cms/modules/pages/details.php