Targetting script bug. (Javascript)

Hi everybody, I'm learning Unity and now I'm trying to do a Targetting script. For now it runs well but there is a little problem that I can't find. When I target an enemy it becames red when i look for him but if i don't look to anybody it should be all white. Most of time it works right but sometime one comes selected when all should be white. Can someone help me?

I have done a empty project with an example so it's easy to see the problem and try it out.

Link to download: https://mega.co.nz/#!RpByCapB!NVxRFW...0L9yH9qt6mIDgc

Key: NVxRFWxKx_Gv7663j1moXi13xWFw30L9yH9qt6mIDgc (shouldn't be needed)

Thanks in advance