fixed bug 3491, ie not need for a crossproduct if both left and right are only expressions, not relations.
fixed bug 3491, ie not need for a crossproduct if both left and right are only expressions, not relations.

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