[Tracker] Sometimes it "forgets" icons until redraws are needed

[bipolar]

I've been noticing this since... at least 2/4 months I guess. It is sporadic, and I usually forget to take a screenshot before the missing icons are redrawn properly (draging any other window in front of the missing icons fixes it, for example).

Attaching a screenshot of the sporadic, but frequent enough to notice, "missing icons in Tracker" I see on my system (64 bits, hrev56112 and hrev56140, but has been here in nightlies for several months at least). .

Don't remember seing that on beta3.

Edit: And... just after minimizing Webpositive, I saw some missing icons on the Desktop :-) As usual, a quick forced redraw fixed it.

Edit 2: I have the "Generate image thumbnails" Tracker option disabled, in case that changes something.