fix the iter column for functions pf:documents and pf:documents(str) to produce the correct results when an iteration step produce empty result.
fix the iter column for functions pf:documents and pf:documents(str) to produce
the correct results when an iteration step produce empty result.

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