make sure insert_string_bat handles inserting a void,str bat into a oid,str bat.
make sure insert_string_bat handles inserting a void,str bat into
a oid,str bat.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb