Defend against null input in analyze_requires_snapshot(), per report from Rushabh Lathia.
Defend against null input in analyze_requires_snapshot(), per report
from Rushabh Lathia.

yuanzhao/gpdb,50wu/gpdb,ashwinstar/gpdb,yazun/postgres-xl,Postgres-XL/Postgres-XL,oberstet/postgres-xl,greenplum-db/gpdb,adam8157/gpdb,postmind-net/postgres-xl,oberstet/postgres-xl,yuanzhao/gpdb,Postgres-XL/Postgres-XL,ovr/postgres-xl,ovr/postgres-xl,greenplum-db/gpdb,postmind-net/postgres-xl,edespino/gpdb,adam8157/gpdb,techdragon/Postgres-XL,edespino/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,yazun/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,snaga/postgres-xl,kmjungersen/PostgresXL,50wu/gpdb,adam8157/gpdb,zeroae/postgres-xl,techdragon/Postgres-XL,ashwinstar/gpdb,yuanzhao/gpdb,Chibin/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,pavanvd/postgres-xl,tpostgres-projects/tPostgres,50wu/gpdb,edespino/gpdb,xinzweb/gpdb,snaga/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,snaga/postgres-xl,oberstet/postgres-xl,zeroae/postgres-xl,jmcatamney/gpdb,edespino/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,jmcatamney/gpdb,Chibin/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,snaga/postgres-xl,techdragon/Postgres-XL,techdragon/Postgres-XL,edespino/gpdb,tpostgres-projects/tPostgres,arcivanov/postgres-xl,edespino/gpdb,Chibin/gpdb,zeroae/postgres-xl,pavanvd/postgres-xl,yuanzhao/gpdb,yazun/postgres-xl,greenplum-db/gpdb,lisakowen/gpdb,Chibin/gpdb,jmcatamney/gpdb,ovr/postgres-xl,xinzweb/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,ovr/postgres-xl,greenplum-db/gpdb,tpostgres-projects/tPostgres,kmjungersen/PostgresXL,lisakowen/gpdb,xinzweb/gpdb,zeroae/postgres-xl,50wu/gpdb,yuanzhao/gpdb,edespino/gpdb,ovr/postgres-xl,ashwinstar/gpdb,yazun/postgres-xl,greenplum-db/gpdb,50wu/gpdb,postmind-net/postgres-xl,edespino/gpdb,adam8157/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,adam8157/gpdb,ashwinstar/gpdb,50wu/gpdb,tpostgres-projects/tPostgres,arcivanov/postgres-xl,kmjungersen/PostgresXL,snaga/postgres-xl,ashwinstar/gpdb,arcivanov/postgres-xl,Chibin/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,edespino/gpdb,yazun/postgres-xl,yuanzhao/gpdb,lisakowen/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,oberstet/postgres-xl,ashwinstar/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,yuanzhao/gpdb,adam8157/gpdb,lisakowen/gpdb,yuanzhao/gpdb,arcivanov/postgres-xl,xinzweb/gpdb,Chibin/gpdb,jmcatamney/gpdb,postmind-net/postgres-xl,Chibin/gpdb,techdragon/Postgres-XL,yuanzhao/gpdb,Chibin/gpdb,Chibin/gpdb,xinzweb/gpdb,edespino/gpdb,50wu/gpdb,arcivanov/postgres-xl,greenplum-db/gpdb,lisakowen/gpdb,arcivanov/postgres-xl,greenplum-db/gpdb,Chibin/gpdb,xinzweb/gpdb