Blender Git Loki

Fix T76996: Don't allow baking when domain is not in object mode

This does not work, because the fluid modifier is not called when the
object is e.g. in edit mode. Another possible fix would be to switch
to object mode when baking starts automatically. However, I think it
is reasonable to simply not allow baking while the domain is in edit mode.

Reviewers: sebbas

Differential Revision: https://developer.blender.org/D7848