Small graphics glitch

[psiweapon]

In my city view, I've got a mine in the topmost corner and it shows one of these little square dots that show while the engine is loading tiles when selecting a building for construction or rotating it.

The dot is showing right on top of the topmost tile of the mine.

[Rasteroid]

Does it go away when you refresh? Is it actually replacing part of the mine?

I need to handle graphics loading better to avoid those white squares.