Bitcode: Do not remove empty summary entries when reading a per-module summary.

This became no longer necessary after D19462 landed, and will be incompatible
with an upcoming change to the summary data structures that changes how we
represent references.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301660 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed