Don't use zend_try around dtor_obj() and free_obj()

Don't use zend_try around dtor_obj() and free_obj()

Without these zend_trys we may
a) leak the object (fine)
b) don't add it to the free list (also fine, we just lose an
   object store bucket)
c) don't remove it from the GC root buffer (also fine, because GC
   explicitly checks for both FREE_CALLED and invalid buckets)