RegisterContextLLDB.cpp (InitializeNonZerothFrame): If we get a

0 mid-stack, stop backtracing.

SectionLoadList.cpp (ResolveLoadAddress): Don't assert on an
out-of-range address, just return an invalid Address object.
The unwinder may be passing in invalid addresses on the final
stack frame and the assert is a problem.

llvm-svn: 122386