RFR: 8303475: potential null pointer dereference in filemap.cpp

[David Holmes]

On Fri, 28 Apr 2023 01:00:50 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

> Please review this small patch which adds an assert in `SharedClassPathEntry::copy_from()` to ensure the input arg `SharedClassPathEntry* ent` is non null. This suppresses a warning from an internal static analysis tool.
> 
> Passed tiers 1 and 3 testing.

Fine and trivial.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/13708#pullrequestreview-1405221519