Undefined property: stdClass::$subject in block.tpl.php

When rendering a block with an empty title via Panels, I'm getting the following notices:

Notice: Undefined property: stdClass::$subject in omega_alpha_preprocess_block() (line 212 of /mysite/sites/all/themes/omega/omega/template.php).
Notice: Undefined property: stdClass::$subject in include() (line 1 of /mysite/sites/all/themes/omega/omega/templates/block.tpl.php).
Notice: Undefined property: stdClass::$subject in include() (line 5 of /mysite/sites/all/themes/omega/omega/templates/block.tpl.php).

The attached patch fixes the issue.