Non existing items displayed in Grid mode at the beginning and the end

[Florian Boucault]

An optimisation broke the grid last week: upicek's revision 1098. Unwanted items are displayed at the limits of the grid. It is highly visible when dragging beyond the end of the grid or before the beginning.

Steps to reproduce:
1. Go in any screen using a grid visualisation mode; eg. go to Pictures > Photo Library > Photos
2. Go to the end of the grid, extreme right
3. Drag further

Expected result:
Only black is shown after the last items of the grid. When releasing the button, the grid aligns back to have the last items next to the border of Elisa's window.

Current result:
Non existing items are shown instead of void.

Note: this also happens if you drag before the beginning of the grid.