RFR: JDK-8256258: some missing NULL checks or asserts after CodeCache::find_blob_unsafe [v2]

[Matthias Baesken]

> Most return values of CodeCache::find_blob_unsafe are NULL checked or at least handled by an asserts. However especially on ppc a few are missing and should be added (e.g. in nativeInst_ppc.cpp).

Matthias Baesken has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  JDK-8256258

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1181/files
  - new: https://git.openjdk.java.net/jdk/pull/1181/files/e0156d33..7c196d3e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1181&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1181&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1181.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1181/head:pull/1181

PR: https://git.openjdk.java.net/jdk/pull/1181