fix(navigation_state): fix handling of legacy zoom factors
fix(navigation_state): fix handling of legacy zoom factors

google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer