Fix bug #81343: inconsistent type conversion after closeCursor

S->cols is already freed in the statement destructor and since
caa710037e663fd78f67533b29611183090068b2 the column data is

Fix bug #81343: inconsistent type conversion after closeCursor

S->cols is already freed in the statement destructor and since
caa710037e663fd78f67533b29611183090068b2 the column data is only
populated on the first execute() which means that on subsequent
execute()s after closeCursor was called, all meta-data for column types
was removed and never restored

Closes GH-7355.

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