We have this:
With other statements, we changed the "unsupported statement" message you get when you attempt to edit - it is now only shown for properties whose datatype we don't support yet.
However, 'depicts' gets added to the page automatically - without value.
The code that currently detects what is supported, uses the statement (in this case: no value) to determine whether the datatype is supported.
Because it has no value, it figures this is not a supported datatype, and grays out the depicts widget and shows a warning when attempting to edit.
We want this:
Nothing - "depicts" is supported
Can be tested on https://commons.wikimedia.beta.wmflabs.org/wiki/File:VisualEditor_toolbar_actions-fur.png
 (if there are no existing 'depicts' statements) the depicts widgets must not be grayed out
 (if there are no existing 'depicts' statements) when clicking 'edit' in depicts widget, one must not get an "Unsupported property" popup