Fix Coverity Scan Issue for PLJAVA
Fix Coverity Scan Issue for PLJAVA

A PL/JAVA NULL point reference has been reported by coverity scan.
The issue is located in guc.c for a pljava guc option
"pljava_classpath_insecure" and fixed in this commit.
lisakowen/gpdb,Chibin/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,50wu/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,adam8157/gpdb,Chibin/gpdb,adam8157/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,jmcatamney/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,lisakowen/gpdb,Chibin/gpdb,Chibin/gpdb,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,50wu/gpdb,lisakowen/gpdb,ashwinstar/gpdb,Chibin/gpdb,xinzweb/gpdb,Chibin/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,jmcatamney/gpdb,50wu/gpdb,Chibin/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,Chibin/gpdb,jmcatamney/gpdb,lisakowen/gpdb,50wu/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,Chibin/gpdb,50wu/gpdb,lisakowen/gpdb,ashwinstar/gpdb,xinzweb/gpdb,greenplum-db/gpdb,Chibin/gpdb,lisakowen/gpdb,xinzweb/gpdb