8189633: Missing -Xcheck:jni checking for DeleteWeakGlobalRef
Summary: Added validity check on the handle before deleting it.
Reviewed-by: dholmes, dcubed
/build/
/dist/
/.idea/
nbproject/private/
/webrev
/.src-rev
/.jib/
.DS_Store
.metadata/
.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
**/JTreport/**
**/JTwork/**