SCUMM: Remove unnecessary NULL check, CID 1003627

Since ah->data is an array, it can't ever be NULL.
SCUMM: Remove unnecessary NULL check, CID 1003628

Since ah->data is an array, it can't ever be NULL.
SCUMM: Remove unnecessary NULL check, CID 1003629

Since _actors[i]->_sound is an array, it can't ever be NULL.