Blender Git Loki

Fix T62377: Crash hiding Armature in edit mode and switching to pose

The poll function accepts hidden objects, so they are not stuck in pose
mode, but the operator itself expects a valid base, which we don't have.

When called from OBJECT_OT_mode_set() it will fallback to object mode.

It is the same that happens when in Edit Mesh mode with a hidden active
object and trying to change to Vertex Painting mode.