Unexpected appearance/behaviour for unchanged opening hours

[ltog]

If you open some opening hours in the opening hours editor and scroll to the bottom (without changing any values), you can't click SAVE although the button looks, like you should be able to save. A very close look reveals that a drop shadow below the button indicates whether it is clickable or not:

I don't consider this appearance/behaviour comprehensible or intuitive and propose one the following changes:

1. Change the font color of inactive buttons to something like gray. (Not sure if this is possible.)
2. Show some kind of popup message telling the user that saving is not possible since no changes were done.
3. Close the opening hours editor and keep the previous (=current) values.