Comment 5 for bug 1671877

Thank you very much, Mc!

And so sorry for the dirty patch :( I'm very new to programming and especially to C++. I now clearly see, that the name of a private variable `_sw_unit` is used wrong. Probably it'll be better to introduce new variable or a function for getting current units.

If you don't mind I'll soon make some corrections to the patch. Thank you.