Do not show error popup on failed automatic update checks

[laeubi]

I get regularly this popup

the error log does not contain any stacktrace and there is not really something a user can act on so this poup should simply not be shown.

[laeubi]

I now looked into this a bit and it is quite strange as this error is generated actually if a status is not set (for whatever reasons)....

One example is org.eclipse.equinox.internal.p2.engine.DownloadManager.filterUnfetched() where it seem to fail for something else (e.g. can't reach repository at all ?) where the one is a MirrorRequest. So if the request is never tried it claims no repository contains the artifact what of course is nonsense.