Fix sliceview debug mode
Fix sliceview debug mode

janelia-flyem/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,janelia-flyem/neuroglancer