PSS llvm: don't abort in getConstant()
PSS llvm: don't abort in getConstant()

we'd like to return it null, so that we can test if
we have a node created. Abort in getOperand() if
we won't get the constant (so nothing will change
in PSS.cpp)

Signed-off-by: Marek Chalupa <a05df156a69ad59faa9af9b666ef78009594c145@gmail.com>

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg