Notice: Undefined variable: rdf_namespaces

Hello guys.
I have a problem with registration (for users). When new user register on the site, there appears the follow information:

Notice: Undefined variable: rdf_namespaces in .../sites/all/themes/education/light/tpl/maintenance-page.tpl.php on line 45

I have tried to change the theme. And got follow errors:
Warning: Illegal offset type in isset or empty in VariableRealmDefaultController->getStore() (line 267 of sites/all/modules/variable/variable_realm/variable_realm.class.inc).
Warning: Illegal offset type in VariableRealmDefaultController->setStore() (line 294 of sites/all/modules/variable/variable_realm/variable_realm.class.inc).
Warning: Illegal offset type in isset or empty in variable_store() (line 15 of sites/all/modules/variable/variable_store/variable_store.module).
Recoverable fatal error: Object of class stdClass could not be converted to string in _variable_store_load() (line 103 of /sites/all/modules/variable/variable_store/variable_store.module).

This errors begin to appear after updating variable module.
Please help, if you can.