Null Reference Exception when deleting a virtual camera

Pretty easy to repro this

I have a scene with a cinemachine brain and a single virtual camera. If I duplicate that virtual camera the new one will take priority as it should.

deactivating the new virtual camera will cause priority to return to the original as expected, but if the new one is deleted I will get a null reference exception every frame forevermore. Seems like destroying a virtual camera should have the same effect as deactivating it