Fix a thinko introduced into CountActiveBackends by a recent patch: we should ignore NULL array entries, not non-NULL ones.  This had the effect of disabling commit_delay, and could have caused a crash in the rare race condition the patch was intended to fix.
Fix a thinko introduced into CountActiveBackends by a recent patch:
we should ignore NULL array entries, not non-NULL ones.  This had the
effect of disabling commit_delay, and could have caused a crash in the
rare race condition the patch was intended to fix.

Bug report and diagnosis by Jeff Janes, in bug #4952.

xuegang/gpdb,greenplum-db/gpdb,zaksoup/gpdb,zaksoup/gpdb,Quikling/gpdb,cjcjameson/gpdb,adam8157/gpdb,janebeckman/gpdb,edespino/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,royc1/gpdb,yuanzhao/gpdb,royc1/gpdb,lintzc/gpdb,cjcjameson/gpdb,Quikling/gpdb,Chibin/gpdb,Quikling/gpdb,adam8157/gpdb,CraigHarris/gpdb,zaksoup/gpdb,Quikling/gpdb,cjcjameson/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,chrishajas/gpdb,greenplum-db/gpdb,Chibin/gpdb,ashwinstar/gpdb,lisakowen/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,Chibin/gpdb,Chibin/gpdb,royc1/gpdb,xuegang/gpdb,zaksoup/gpdb,xuegang/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,rvs/gpdb,ahachete/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,janebeckman/gpdb,xuegang/gpdb,Quikling/gpdb,xuegang/gpdb,janebeckman/gpdb,0x0FFF/gpdb,0x0FFF/gpdb,ahachete/gpdb,jmcatamney/gpdb,edespino/gpdb,chrishajas/gpdb,Chibin/gpdb,ashwinstar/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,Quikling/gpdb,yuanzhao/gpdb,janebeckman/gpdb,rvs/gpdb,Quikling/gpdb,CraigHarris/gpdb,zaksoup/gpdb,royc1/gpdb,lisakowen/gpdb,50wu/gpdb,janebeckman/gpdb,0x0FFF/gpdb,xuegang/gpdb,xinzweb/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,chrishajas/gpdb,royc1/gpdb,rvs/gpdb,lintzc/gpdb,lisakowen/gpdb,cjcjameson/gpdb,edespino/gpdb,rvs/gpdb,Chibin/gpdb,50wu/gpdb,janebeckman/gpdb,lintzc/gpdb,zaksoup/gpdb,adam8157/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,chrishajas/gpdb,xinzweb/gpdb,Quikling/gpdb,lisakowen/gpdb,50wu/gpdb,xuegang/gpdb,adam8157/gpdb,lisakowen/gpdb,0x0FFF/gpdb,adam8157/gpdb,rvs/gpdb,CraigHarris/gpdb,50wu/gpdb,lintzc/gpdb,edespino/gpdb,adam8157/gpdb,kaknikhil/gpdb,xinzweb/gpdb,zaksoup/gpdb,ahachete/gpdb,royc1/gpdb,cjcjameson/gpdb,xinzweb/gpdb,royc1/gpdb,Chibin/gpdb,jmcatamney/gpdb,ahachete/gpdb,edespino/gpdb,rvs/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,rvs/gpdb,edespino/gpdb,xuegang/gpdb,rvs/gpdb,edespino/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,adam8157/gpdb,kaknikhil/gpdb,0x0FFF/gpdb,0x0FFF/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,chrishajas/gpdb,CraigHarris/gpdb,Chibin/gpdb,jmcatamney/gpdb,cjcjameson/gpdb,edespino/gpdb,xinzweb/gpdb,janebeckman/gpdb,janebeckman/gpdb,edespino/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,CraigHarris/gpdb,zaksoup/gpdb,cjcjameson/gpdb,yuanzhao/gpdb,ahachete/gpdb,cjcjameson/gpdb,lintzc/gpdb,CraigHarris/gpdb,janebeckman/gpdb,cjcjameson/gpdb,chrishajas/gpdb,ashwinstar/gpdb,janebeckman/gpdb,50wu/gpdb,greenplum-db/gpdb,CraigHarris/gpdb,lintzc/gpdb,lintzc/gpdb,xinzweb/gpdb,rvs/gpdb,lisakowen/gpdb,Chibin/gpdb,rvs/gpdb,yuanzhao/gpdb,ahachete/gpdb,50wu/gpdb,50wu/gpdb,0x0FFF/gpdb,royc1/gpdb,Chibin/gpdb,0x0FFF/gpdb,ahachete/gpdb,chrishajas/gpdb,xinzweb/gpdb,lintzc/gpdb,adam8157/gpdb,lintzc/gpdb,chrishajas/gpdb,50wu/gpdb,cjcjameson/gpdb,edespino/gpdb,xuegang/gpdb,yuanzhao/gpdb,ahachete/gpdb,Quikling/gpdb,lisakowen/gpdb,Quikling/gpdb