#56 "Cannot check free space" should be warning not error

[GodzillaXP]

When writing an image to a samba share, I get an error, because the available free disk spave cannot be read.

While the message reads correctly "checking free disk space will be skipped" (I get the message in german), I think the big red error-icon is confusing.

This should be a warning not an error, because the main function of the program is executed correctly.

[Tobin Davis]

I'll look into this for the next release. Note that I am going to try to get a release soon without any UI changes so that I don't need to get new translations done. This shouldn't impact translations, but I will need to verify.