Convering NULL to nullptr
Convering NULL to nullptr

Converting to C++11 standard

Refs idaholab/relap-7#19688
milljm/moose,andrsd/moose,harterj/moose,laagesen/moose,idaholab/moose,bwspenc/moose,dschwen/moose,andrsd/moose,lindsayad/moose,laagesen/moose,harterj/moose,dschwen/moose,lindsayad/moose,bwspenc/moose,sapitts/moose,harterj/moose,dschwen/moose,dschwen/moose,bwspenc/moose,sapitts/moose,harterj/moose,sapitts/moose,idaholab/moose,jessecarterMOOSE/moose,laagesen/moose,jessecarterMOOSE/moose,idaholab/moose,andrsd/moose,milljm/moose,idaholab/moose,lindsayad/moose,bwspenc/moose,andrsd/moose,dschwen/moose,milljm/moose,harterj/moose,sapitts/moose,sapitts/moose,laagesen/moose,bwspenc/moose,lindsayad/moose,andrsd/moose,jessecarterMOOSE/moose,jessecarterMOOSE/moose,jessecarterMOOSE/moose,idaholab/moose,milljm/moose,laagesen/moose,milljm/moose,lindsayad/moose