fix(extend_segments_tool): correct use of neuroglancer API
fix(extend_segments_tool): correct use of neuroglancer API

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