[PATCH v1] PL/Perl: Fix NULL deref for forged array

Hi hackers,

A PL/Perl function returning a forged PostgreSQL::InServer::ARRAY
object (e.g., an empty hash blessed as that class) could cause a
segfault. This occurs because hv_fetch_string returns NULL pointer
when the "array" key is missing, and the code previously dereferenced
it without checking if the pointer itself was NULL.

The attachment is the patch for fixing it.

Best Regards,
Xing