RFR: 8297801: printnm crashes with invalid address due to null pointer dereference [v2]

[Damon Fenacci]

> `printnm` crashes if you pass an invalid address. This is caused by a null pointer dereference.
> Checking for NULL reference before checking if blob is a method.

Damon Fenacci has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8297801: print message when address invalid

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11697/files
  - new: https://git.openjdk.org/jdk/pull/11697/files/e6c06762..7a93cadd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11697&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11697&range=00-01

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11697.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11697/head:pull/11697

PR: https://git.openjdk.org/jdk/pull/11697