- Removed dubious code in MaterialEditor.cpp that prevented orphaned nodes to be deleted.
- Unified calls to Material->Modify() to MaterialModify() to make sure Modify() is called on the material and its editor only data, as well as the edited material function (if any) and its editor only data.
#jira UE-219651
#rb Jason.Nadro, Jon.Cain
#rn Fixed an issue that caused frequent crashes when performing delete, undo, and redo operations on Material Expressions, especially when these operations were applied to Function Inputs while a material using the Function was open in the editor.
#review https://p4-swarm.epicgames.net/reviews/36794197
#review https://p4-swarm.epicgames.net/reviews/36856173
[CL 37052446 by massimo tristano in 5.5 branch]
799d3343e2