encoding error for BLOB SUB TYPE TEXT

[holev45]

Hi.
For encoding text driver uses charset send in connect string and this can be wrong.
I use UTF8 and almost everything works fine - except BLOB TEXT, when change to WIN1250/cp1250 almost everything goes wrond except the BLOB TEXT. To correct this I extend line 3856 in: src/firebird/driver/core.py
from:
value = value.decode(self._encoding)

to:
try:
value = value.decode(self._encoding)
except:
value = value.decode(CHARSET_MAP.get(self._connection.info.charset))

Mostly because I didnt find better solution.