Avoid out-of-bounds read in errfinish if error_stack_depth < 0.
Avoid out-of-bounds read in errfinish if error_stack_depth < 0.

If errordata_stack_depth < 0, we won't find that out and correct the
problem until CHECK_STACK_DEPTH() is invoked.  In the meantime,
elevel will be set based on an invalid read.  This is probably
harmless in practice, but it seems cleaner this way.

Xi Wang

greenplum-db/gpdb,Postgres-XL/Postgres-XL,50wu/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,ovr/postgres-xl,greenplum-db/gpdb,adam8157/gpdb,zeroae/postgres-xl,yazun/postgres-xl,techdragon/Postgres-XL,ashwinstar/gpdb,ashwinstar/gpdb,50wu/gpdb,xinzweb/gpdb,50wu/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,yazun/postgres-xl,xinzweb/gpdb,adam8157/gpdb,jmcatamney/gpdb,yazun/postgres-xl,ovr/postgres-xl,Postgres-XL/Postgres-XL,lisakowen/gpdb,Postgres-XL/Postgres-XL,adam8157/gpdb,adam8157/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,xinzweb/gpdb,ovr/postgres-xl,adam8157/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,ashwinstar/gpdb,oberstet/postgres-xl,oberstet/postgres-xl,lisakowen/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,50wu/gpdb,50wu/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,techdragon/Postgres-XL,zeroae/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,jmcatamney/gpdb,Postgres-XL/Postgres-XL,50wu/gpdb,techdragon/Postgres-XL,jmcatamney/gpdb,ovr/postgres-xl,adam8157/gpdb,oberstet/postgres-xl,50wu/gpdb,pavanvd/postgres-xl,zeroae/postgres-xl,yazun/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,greenplum-db/gpdb,ovr/postgres-xl,adam8157/gpdb,adam8157/gpdb,oberstet/postgres-xl,lisakowen/gpdb,lisakowen/gpdb,ashwinstar/gpdb,yazun/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,techdragon/Postgres-XL,ashwinstar/gpdb