fix(null-safety): Add null checks in various segmentation related code.#2550

jbocce merged 1 commit intocornerstonejs:maincornerstonejs/cornerstone3D:mainfrom

jbocce:fix/OHIF-2200-segment-after-capturejbocce/cornerstone3D-beta:fix/OHIF-2200-segment-after-captureCopy head branch name to clipboard