[DAGCombiner] Add two calls to isVector before making calls to getVectorElementType/getVectorNumElements to avoid an assert.

We looked through a BITCAST, but the bitcast might be a from a scalar type rather than a vector.

I don't have a test case. I stumbled onto it while prototyping another change that isn't ready yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325750 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed