qmol_from_smiles() + bogus input causes engine crash

[robins]

Describe the bug
Similar to #3687 and #3688, engine crash when calling mol_adjust_query_properties() with bogus input

To Reproduce
SELECT mol_adjust_query_properties(nullif(NULL::mol, NULL::mol)::mol, 'a'::cstring) @> qmol_from_smiles('a'::cstring);

Screenshots / SQL Output

postgres=> SELECT mol_adjust_query_properties(nullif(NULL::mol, NULL::mol)::mol, 'a'::cstring) @> qmol_from_smiles('a'::cstring);
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!?> \q

Error Log Excerpt

2021-01-04 08:06:48 UTC::@:[20623]:LOG: server process (PID 20539) was terminated by signal 11: Segmentation fault
2021-01-04 08:06:48 UTC::@:[20623]:DETAIL: Failed process was running: SELECT mol_adjust_query_properties(nullif(NULL::mol, NULL::mol)::mol, 'a'::cstring) @> qmol_from_smiles('a'::cstring);
2021-01-04 08:06:48 UTC::@:[20623]:LOG: terminating any other active server processes

[greglandrum]

I think the problem here is actually with qmol_from_smiles.
Breaking your reproducible into two pieces shows this:

egression=# SELECT mol_adjust_query_properties(nullif(NULL::mol, NULL::mol)::mol, 'a'::cstring);
 mol_adjust_query_properties 
-----------------------------
 
(1 row)

regression=# SELECT qmol_from_smiles('a'::cstring);
server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!> 

If you can confirm I will rename the issue.

[robins]

Thanks for looking into this promptly.

I didn't know the relation but Correct, SELECT qmol_from_smiles('a'::cstring); crashes too.

postgres=> SELECT qmol_from_smiles('a'::cstring);
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!?> \q

[robins]

! A little more coffee and now I see what I missed earlier. Updated the Issue title.