Add some simple defenses against null fields in pg_largeobject, and add comments noting that there's an alignment assumption now that the data field could be in 1-byte-header format.  Per discussion with Greg Stark.
Add some simple defenses against null fields in pg_largeobject, and add
comments noting that there's an alignment assumption now that the data
field could be in 1-byte-header format.  Per discussion with Greg Stark.

tpostgres-projects/tPostgres,postmind-net/postgres-xl,janebeckman/gpdb,tpostgres-projects/tPostgres,edespino/gpdb,kaknikhil/gpdb,janebeckman/gpdb,pavanvd/postgres-xl,zaksoup/gpdb,Postgres-XL/Postgres-XL,rvs/gpdb,0x0FFF/gpdb,janebeckman/gpdb,xinzweb/gpdb,postmind-net/postgres-xl,zeroae/postgres-xl,kaknikhil/gpdb,cjcjameson/gpdb,50wu/gpdb,chrishajas/gpdb,zeroae/postgres-xl,kmjungersen/PostgresXL,edespino/gpdb,royc1/gpdb,cjcjameson/gpdb,lintzc/gpdb,Quikling/gpdb,janebeckman/gpdb,rvs/gpdb,lintzc/gpdb,lisakowen/gpdb,royc1/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,adam8157/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,50wu/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,lintzc/gpdb,0x0FFF/gpdb,lintzc/gpdb,postmind-net/postgres-xl,rvs/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,janebeckman/gpdb,Quikling/gpdb,cjcjameson/gpdb,ahachete/gpdb,ashwinstar/gpdb,Quikling/gpdb,lintzc/gpdb,jmcatamney/gpdb,zaksoup/gpdb,edespino/gpdb,royc1/gpdb,janebeckman/gpdb,kaknikhil/gpdb,edespino/gpdb,lisakowen/gpdb,CraigHarris/gpdb,cjcjameson/gpdb,ahachete/gpdb,Chibin/gpdb,kaknikhil/gpdb,chrishajas/gpdb,oberstet/postgres-xl,oberstet/postgres-xl,50wu/gpdb,CraigHarris/gpdb,Quikling/gpdb,chrishajas/gpdb,xuegang/gpdb,xinzweb/gpdb,Quikling/gpdb,yazun/postgres-xl,cjcjameson/gpdb,Postgres-XL/Postgres-XL,jmcatamney/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,Chibin/gpdb,ahachete/gpdb,edespino/gpdb,techdragon/Postgres-XL,zaksoup/gpdb,cjcjameson/gpdb,pavanvd/postgres-xl,0x0FFF/gpdb,chrishajas/gpdb,kmjungersen/PostgresXL,janebeckman/gpdb,edespino/gpdb,techdragon/Postgres-XL,50wu/gpdb,arcivanov/postgres-xl,adam8157/gpdb,Quikling/gpdb,oberstet/postgres-xl,50wu/gpdb,xinzweb/gpdb,lintzc/gpdb,edespino/gpdb,snaga/postgres-xl,yazun/postgres-xl,0x0FFF/gpdb,kaknikhil/gpdb,janebeckman/gpdb,adam8157/gpdb,kmjungersen/PostgresXL,yuanzhao/gpdb,kaknikhil/gpdb,tpostgres-projects/tPostgres,ahachete/gpdb,adam8157/gpdb,kmjungersen/PostgresXL,pavanvd/postgres-xl,50wu/gpdb,ovr/postgres-xl,yuanzhao/gpdb,xuegang/gpdb,adam8157/gpdb,kaknikhil/gpdb,pavanvd/postgres-xl,yuanzhao/gpdb,lintzc/gpdb,zeroae/postgres-xl,royc1/gpdb,zeroae/postgres-xl,jmcatamney/gpdb,Chibin/gpdb,Chibin/gpdb,cjcjameson/gpdb,snaga/postgres-xl,kaknikhil/gpdb,arcivanov/postgres-xl,royc1/gpdb,chrishajas/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,chrishajas/gpdb,Quikling/gpdb,rvs/gpdb,Chibin/gpdb,ahachete/gpdb,ovr/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,ovr/postgres-xl,ashwinstar/gpdb,CraigHarris/gpdb,kaknikhil/gpdb,rvs/gpdb,cjcjameson/gpdb,chrishajas/gpdb,lintzc/gpdb,royc1/gpdb,snaga/postgres-xl,Quikling/gpdb,jmcatamney/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,xinzweb/gpdb,0x0FFF/gpdb,ovr/postgres-xl,zaksoup/gpdb,jmcatamney/gpdb,adam8157/gpdb,arcivanov/postgres-xl,yazun/postgres-xl,xuegang/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,rvs/gpdb,Quikling/gpdb,ahachete/gpdb,jmcatamney/gpdb,lisakowen/gpdb,Chibin/gpdb,50wu/gpdb,0x0FFF/gpdb,xinzweb/gpdb,greenplum-db/gpdb,snaga/postgres-xl,xinzweb/gpdb,edespino/gpdb,arcivanov/postgres-xl,xuegang/gpdb,royc1/gpdb,royc1/gpdb,yuanzhao/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xuegang/gpdb,edespino/gpdb,techdragon/Postgres-XL,rvs/gpdb,postmind-net/postgres-xl,greenplum-db/gpdb,kmjungersen/PostgresXL,CraigHarris/gpdb,adam8157/gpdb,xuegang/gpdb,ahachete/gpdb,ovr/postgres-xl,zaksoup/gpdb,ashwinstar/gpdb,rvs/gpdb,yuanzhao/gpdb,xuegang/gpdb,zaksoup/gpdb,Chibin/gpdb,arcivanov/postgres-xl,edespino/gpdb,chrishajas/gpdb,snaga/postgres-xl,Quikling/gpdb,Chibin/gpdb,techdragon/Postgres-XL,zaksoup/gpdb,rvs/gpdb,yazun/postgres-xl,oberstet/postgres-xl,zaksoup/gpdb,greenplum-db/gpdb,lisakowen/gpdb,xuegang/gpdb,zeroae/postgres-xl,tpostgres-projects/tPostgres,ashwinstar/gpdb,xuegang/gpdb,techdragon/Postgres-XL,postmind-net/postgres-xl,Chibin/gpdb,yazun/postgres-xl,kaknikhil/gpdb,xinzweb/gpdb,ashwinstar/gpdb,ahachete/gpdb,rvs/gpdb,tpostgres-projects/tPostgres,Postgres-XL/Postgres-XL,CraigHarris/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,lisakowen/gpdb,Chibin/gpdb,arcivanov/postgres-xl,lintzc/gpdb,janebeckman/gpdb,lisakowen/gpdb,oberstet/postgres-xl,Postgres-XL/Postgres-XL,CraigHarris/gpdb,janebeckman/gpdb