Fix a crash that happens when mapping something like this:

Fix a crash that happens when mapping something like this:

 { short, short }

to
  short

where the second short maps onto the second field of the first struct.  In
this case, the struct index is not aligned, so we should avoid calling
getLink(2), which asserts out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20626 91177308-0d34-0410-b5e6-96231b3b80d8