Ensure lastrowid value exists before trying to assign it

[hab6]

Description

Fix that avoids trying to assign a value in cases where no value exists after calling the Ingres LAST_IDENTITY function during SQL post processing.

Prevents error: TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType' when running a number of tests.

Environment

Ingres 11.2 (15807) on Windows 10 (client & server are same)
Python 3.10.7
mock 5.1.0
packaging 24.0
pip 24.0
pluggy 1.5.0
pyodbc 5.1.0
pypyodbc 1.3.6
pytest 8.2.0
setuptools 63.2.0
SQLAlchemy 2.0.29.dev0
sqlalchemy-ingres 0.0.7.dev1
tox 4.15.0

Related ticket: II-14233

Results using various tests from the SQLAlchemy dialect compliance suite

WITHOUT FIX	Pass	Fail
BinaryTest	0	3
DateTest	2	4
DateTimeCoercedToDateTimeTest	2	4
DateTimeMicrosecondsTest	0	5
DateTimeTest	2	4
DifficultParametersTest	42	21
IntegerTest	1	22
IsOrIsNotDistinctFromTest	0	5
Results without fix	49	68

WITH FIX	Pass	Fail
BinaryTest	3	0
DateTest	6	0
DateTimeCoercedToDateTimeTest	6	0
DateTimeMicrosecondsTest	2	3 (a)
DateTimeTest	6	0
DifficultParametersTest	63	0
IntegerTest	12	11 (b)
IsOrIsNotDistinctFromTest	5	0
Results with fix	103	14

(a) Different error now occurs: AssertionError
(b) Different error now occurs due to unrelated bad SQL syntax

[mianculovici]

Approved.