VM crashes with "guarantee(last != NULL) failed: last may not be null" when running with -XX:+VerifyStack after JDK-8284161 (debug build only).

Can be reproduced in tests like:
compiler/c2/cr6589834/Test_ia32.java
testlibrary_tests/ir_framework/tests/TestDFlags.java
compiler/uncommontrap/TestDeoptOOM.java
compiler/interpreter/TestVerifyStackAfterDeopt.java
compiler/interpreter/VerifyStackWithUnreachableBlock.java

Stack frames get analyzed in Deoptimization::unpack_frames which is a JRT_LEAF function. That doesn't work reliably in general and currently doesn't work on PPC64 because the deoptimization and uncommon trap stubs don't set the last Java PC to where the OopMaps are.