Undo & selection-zoom buttons on graph stay active after their action

[evertrol]

When clicking on the undo or selection-zoom button on a graph (even when there is no undo action possible, or no selection to zoom in to), the icon stays selected (grey background instead of transparent), until another action is performed.
This other action may be a click elsewhere, or moving the pointer out of the graph area. Focusing another browser tab or window does not clear it, though: the action has to be in the current tab.

This is just a minor issue, and likely won't cause any confusion.