RFR: 8259403: Zero: crash with NULL MethodHandle receiver

[Aleksey Shipilev]

Happens reliably:

$ CONF=linux-x86_64-zero-fastdebug make exploded-test TEST=compiler/jsr292/NullConstantReceiver.java
# A fatal error has been detected by the Java Runtime Environment:
# SIGSEGV (0xb) at pc=0x0000000000000000, pid=4059994, tid=4060008

Zero's MH handling code does not check if receiver is NULL before accessing its klass.

Additional testing:
 - [x] Linux x86_64 Zero `compiler/jsr292/NullConstantReceiver.java`
 - [x] Linux x86_64 Zero `tier1` (no new failures)

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Commit messages:
 - 8259403: Zero: crash with NULL MethodHandle receiver

Changes: https://git.openjdk.java.net/jdk/pull/1987/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1987&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259403
  Stats: 79 lines in 4 files changed: 57 ins; 16 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1987.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1987/head:pull/1987

PR: https://git.openjdk.java.net/jdk/pull/1987