How to reproduce:
1. Open the attached '1305089.zip' project
2. In the Project window double-click on the 'AnimatedSpriteDissolve' Shader Graph
3. Select one of the nodes and try to drag it
4. Observe the Console

Expected result: No visible errors present
Actual result: The 'ArgumentNullException' error gets thrown in the Console, the node sticks to the mouse cursor

Reproducible with: Shader Graph 10.2.0 (2020.2.2f1, 2021.1.0b3), 11.0.0 (2021.1.0b3, 2021.2.0a2)
Not reproducible with: Shader Graph 7.5.2 (2019.4.18f1), 10.1.0 (2020.2.2f1, 2021.1.0b3)
Cannot test with: Shader Graph 4.10.0-preview (the Shader Graph can't be opened in the Shader Editor), 10.1.0, 10.2.0 (2021.2.0a2), 11.0.0 (2020.2.2f1) (due to the package errors)

Notes:
- The following error gets thrown in the Console:
ArgumentNullException: Value cannot be null.
Parameter name: identifier
- The same error gets thrown when trying to create, delete, duplicate nodes, delete, connect edges, rename Properties and Keywords (none of these actions get performed)
- Information about the node is not displayed in the Graph Inspector (Node Settings) when the node is selected
- When trying to drag the node it sticks to the mouse cursor (until the ESC, mouse wheel, or the right mouse button is pressed)