Fix PointSprite panel.

Continues on the fix made by 7017d50ab0c3d8481fbca73c7352057299c422cf. We were
missing panel_widget specifications on non-polygonal representations. Fixed
that.

Change-Id: I9a6579a76ff5c124ad9b762c407431aabec13b87
Merge topic 'fix_pointsprite_plugin' into next

8dc44de Fix PointSprite panel.