[aarch64-port-dev ] RFR: Backport: 8209413: AArch64: NPE in clhsdb jstack command

[Andrew Haley]

This is a somewhat cut-down and adjusted version of Nick Gasson's
patch, which also rearranged code elsewhere.

http://cr.openjdk.java.net/~aph/aarch64-jdk8u/8209413.patch

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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