Supporting object reset while its properties are being iterated would increase
complexity for little benefit. Furthermore it may not be possible to ensure a
consistent behavior between ghosts and proxies (wrt to iteration position).
Iteration is detected by checking if the object's properties ht has iterators.
This requires refactoring the hooked get_iterator() implementation to ensure
that it creates a properties ht iterator immediately.
Closes GH-15960
The return value of zho_build_properties_ex() is passed to ZVAL_ARR(), which sets the IS_TYPE_REFCOUNTED flag. Returning &zend_emtpy_array will crash later when trying to dtor the zval.
I'm fixing this by returning zend_new_array(0) instead of &zend_empty_array.
An alternative was to make ZVAL_ARR() aware of immutable arrays, like ZVAL_STR() is with interned strings, but I found no other problematic cases.
