volume related fixes

src/apps/canvas/index.ts

src/mol-geo/representation/volume/direct-volume.ts

src/mol-gl/shader/direct-volume.frag

src/mol-gl/shader/direct-volume.vert

src/mol-io/reader/ccp4/parser.ts

src/mol-math/geometry/spacegroup/construction.ts

src/mol-model/structure/model/formats/mmcif.ts

src/mol-model/structure/structure/carbohydrates/compute.ts

src/mol-model/volume/data.ts

src/mol-model/volume/formats/ccp4.ts