All new elements except the last one initialized to NULL. Ideally, once parsing is complete, all elements should be non-NULL.
To safe-guard BitcodeReader, this patch adds null check for all access to these list.
Patch by Dinesh Dwivedi!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204920 91177308-0d34-0410-b5e6-96231b3b80d8