RFR: 8371501: Change IAE to NPE in java.awt.image.Kernel when data is null

[Sergey Bylokhov]

This is an update to the patch integrated in https://github.com/openjdk/jdk/pull/28127. It changes the exception from IllegalArgumentException back to NullPointerException, which was thrown previously.

Rationale:
 - Since an NPE was already thrown before, this does not introduce a behavior change
 - Throwing NPE on null is the common pattern used across the codebase, including in the affected package

Additional notes:
The patch uses the idiomatic way to check parameters for null via Objects.requireNonNull(). I am not sure whether this code path is performance critical. The use of >> 1 instead of / 2 suggests that performance might matter. If this code is performance sensitive, we can remove the Objects.requireNonNull() call, because even without it the resulting NPE would still clearly show which variable was null when its field was accessed.

It is also possible to remove the use of multiplyExact(). We can simply multiply width/height as long values and compare the result with the data length. In case of overflow, the existing “Data array too small” exception would still be thrown.

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Commit messages:
 - 8371501: Change IAE to NPE in java.awt.image.Kernel when data is null

Changes: https://git.openjdk.org/jdk/pull/28249/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371501
  Stats: 41 lines in 2 files changed: 18 ins; 6 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/28249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28249/head:pull/28249

PR: https://git.openjdk.org/jdk/pull/28249