Fix display when scrolling quickly among the results

When scrolling quickly among the results, we observe that incorrect thumbnails are displayed for documents before the correct thumbnail is loaded and replaces the incorrect one. With a fast/local network, it's difficult to observe it because the incorrect picture is very quickly replaced, but with slow networks, the behavior is very disturbing.

Steps to reproduce:

1. Create a Folder document
2. Drag and drop the 200 pictures from the archive in the first comment
3. Wait for the conversions to complete
4. Switch to Grid view for the Folder document
5. Scroll down to the middle of the page or a little bit more
6. Open the Developer tools and configure the network throttling to Slow 3G or Regular 2G (Chrome/Firefox)
7. Scroll up and observe that the same row is repeated several times => that's the issue

A video is attached to highlight the behavior.

Expected behavior: when scrolling, if a picture is not loaded, we should see the placeholder and not the picture from another row in the result