bizgres - bizgres: Handle empty statement.

Log Message:
-----------
Handle empty statement. Some housekeping for resource scheduling was assuming
that parsetrees were always non-trivial.

Modified Files:
--------------
    bizgres/postgresql/src/backend/tcop:
        postgres.c (r1.6 -> r1.7)

(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/bizgres/bizgres/postgresql/src/backend/tcop/postgres.c.diff?r1=1.6&r2=1.7)