[guile-dbi] Check finalized-smob properly

[Nala Ginrut]

Hi folks!

*The guile-dbi community intended to discuss issues in guile-user mailing
list, so I just put it here.*

I encountered an error:
----------------------------cut------------------------------
In procedure dbi-close: Wrong type argument in position 1: #<finalized smob
7f54416b8d30>
-----------------------------end----------------------------

My opinion is that the dbi-close doesn't check finalized-smob properly, it
didn't consider it at all.

------------------------code-----------------------------
#define DBI_SMOB_P(obj) ((SCM_NIMP(obj)) &&
(SCM_TYP16(obj)==g_db_handle_tag))
-------------------------end------------------------------

On the other hand, I'm not sure why the SMOB was finalized before dbi-close.

Anyway, my idea to patch dbi-close is to check if it's already finalized,
if yes then just return. However, I didn't find the predicate to check
finalized-smob.

Comments?

Best regards.