Blender Git Loki

Fix T81818: Outliner mode column crashes with shared object data

For objects with shared data, it makes sense to show the mode icon for
every object sharing the same data if one of them is in edit mode.

This also disables the "extend" functionality in this case, because
being in edit mode for multiple objects with the same data isn't
supported.

Differential Revision: https://developer.blender.org/D9273