Hang and log spam when making changes to a landscape material with the landscape editor open

Editor hangs if changes are made to the material which is currently assigned to a landscape while the landscape editor is open.

Also spams "LogMaterial: 0.03 seconds spent updating 1 materials, 1 interfaces, 0 instances, 1 with static permutations."

Probably also affects older versions, but unconfirmed

1. Open QAGame
2. Create a new landscape using the test landscape material
3. open the landscape material while the landscape editor is still open
4. make some change, then press "apply changes"
5. hang