Fix a possible bug where duplicate labels will be created if the loop body contains a label 0.
Fix a possible bug where duplicate labels will be created if the loop body contains a label 0.

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