All toolbar buttons are links. This mean that when the "click" or the mouse events are not stopped, the browser will generally connect to the current page + "#". If an error occurs, the same problem can occur.

Care should therefore be taken to prevent the link from being taken into account at all times.

Moreover, the design of the toolbar buttons should be rethought in a way that handles this kind of thing automatically. Some ideas in the same vein:
1) make use of "button" element rather than anchors
2) contruct the button callbacks from the JS code, as it done for the menus

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3) add enabled/disabled actions