Disable deleting of operators being edited
Disable deleting of operators being edited

This can cause a crash, and is not needed. Operators will be removed if
cancel is clicked, or kept if OK is clicked.

mathturtle/tomviz,OpenChemistry/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,mathturtle/tomviz