RFR: 8285397: JNI exception pending in CUPSfuncs.c:250

[Phil Race]

A tool checking for JNI errors complains that the call to JNU_NewStringPlatform(..)
might throw an exception and subsequent JNI code isn't making sure of that.
Clear the exception so the error handling code can do its thing.

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Commit messages:
 - 8285399

Changes: https://git.openjdk.java.net/jdk/pull/8491/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8491&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285397
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8491.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8491/head:pull/8491

PR: https://git.openjdk.java.net/jdk/pull/8491