Init member to nullptr
Init member to nullptr

cjh1/tomviz,mathturtle/tomviz,thewtex/tomviz,thewtex/tomviz,OpenChemistry/tomviz,mathturtle/tomviz,cjh1/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,cryos/tomviz,cjh1/tomviz,thewtex/tomviz,mathturtle/tomviz,OpenChemistry/tomviz,cryos/tomviz,cryos/tomviz