A few problems were found in the fix for bug 43668:
1) Comparison of the YEAR column with NULL always returned TRUE;
2) Comparison of the YEAR column with constants always returned
   unpredictable result;
3) Unnecessary conversion warnings when comparing a non-integer
   constant with a NULL value in the YEAR column;

The problems described above have been resolved with an
exception: zero (i.e. invalid) YEAR column value comparison
with 00 or 2000 still fail (it is not a regression and it was
not a regression), so MIN/MAX on YEAR column containing zero
value still fail.