How to reproduce:
1. Create a new LWRP/HDRP Project
2. Set it up to use Perforce's version control
3. In the Project Window create a new Shadergraph
4. Double click the graph, make changes and save

Expected result: A dialog is shown, stating that the Shader Graph is currently not editable. In the case of Perforce, if it’s an option to checkout the file to make it editable, allow the user to do so from this dialog.
Actual result: The Shader Graph is checked out and saved without asking the user.

Reproduced with: Shadergraph version 5.7.2; 5.6.1
Not reproducible with: Shadergraph version 5.3.1; 5.2.3

Note: Reproducible with both LWRP and HDRP

Additionally, to reproduce the crash:
1. Make another new Shadergraph and submit it
2. Make sure that it is not checked (Read-only)
3. Disconnect the version control
4. Open the graph, add any new property and close the graph
5. A save prompt will appear, click save
6. Observe the crash

Crash reproduced on: 2019.3.0a2