RFR: 8255563: Missing NULL checks after JDK-8233624

[David Holmes]

On Thu, 5 Nov 2020 01:07:24 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> JDK-8233624 introduced a check for illegal native method names that will result in the `NativeLookup::*_jni_name` methods returning NULL. JVMCI `registerNativeMethods` uses these APIs without any check for a NULL return, however the methods being registered are part of the JVMCI implementation so should never have an illegal name, so adding a guarantee suffices to deal with that (see comments in JBS issue).
>
> Looks good.

@dougxc could you review this please. Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/1068