fix(rtstruct): prevent viewport from becoming blank on second load#5996

Belbin-GK wants to merge 6 commits into

OHIF:masterOHIF/Viewers:masterfrom

Belbin-GK:rtstruct-viewport-blank-on-second-loadBelbin-GK/Viewers:rtstruct-viewport-blank-on-second-loadCopy head branch name to clipboard