Fix #1868 constant lowering of optional value in omitted arg
Fix #1868
constant lowering of optional value in omitted arg

sklam/numba,stonebig/numba,stefanseefeld/numba,sklam/numba,numba/numba,stuartarchibald/numba,stonebig/numba,seibert/numba,gmarkall/numba,jriehl/numba,stonebig/numba,seibert/numba,stuartarchibald/numba,stuartarchibald/numba,jriehl/numba,jriehl/numba,seibert/numba,stuartarchibald/numba,sklam/numba,stuartarchibald/numba,gmarkall/numba,seibert/numba,IntelLabs/numba,sklam/numba,IntelLabs/numba,gmarkall/numba,IntelLabs/numba,numba/numba,cpcloud/numba,gmarkall/numba,IntelLabs/numba,gmarkall/numba,IntelLabs/numba,numba/numba,stefanseefeld/numba,stefanseefeld/numba,numba/numba,jriehl/numba,cpcloud/numba,stonebig/numba,stefanseefeld/numba,cpcloud/numba,cpcloud/numba,seibert/numba,jriehl/numba,cpcloud/numba,numba/numba,stefanseefeld/numba,sklam/numba,stonebig/numba