Follow-up to r199120: don't try referencing the dtor if the param decl isn't valid.

This was caught by running test/SemaCXX/destructor.cpp in MS ABI mode.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199128 91177308-0d34-0410-b5e6-96231b3b80d8
[ms-abi] Quick fix layout of an array of records

This fixes llvm::SmallVector, which fixes lots of TUs in the MS ABI self
host.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199129 91177308-0d34-0410-b5e6-96231b3b80d8