Fix unnest() to handle a toasted input array safely.  Per report from Alvaro.
Fix unnest() to handle a toasted input array safely.  Per report from
Alvaro.

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