Reproduced in SRP master of 8/7/19 (0c3b4b5888), 2019.3.0a12

Repro #1 (with my simple file):
1) Open up DeleteMyNodes.ShaderGraph
2) Box Select the group node and everything inside, as seen in the gif.
3) Delete
> Graph View crashes; data/work is lost.

Repro #2 (if you don't want to DL my file):
1) Create a Shader Graph
2) Create a property for that Shader Graph
3) Place that property within GV
4) Group that single Property Node; a group with 1 node
5) Select both the group node and node inside with box select
6) Delete
> Graph View crashes; data/work is lost.

Error Code: see below