applets/clipboard: fix tool buttons not clickable using stylus
Those buttons are exclusive grabbers for mouse events, but not for other pointer events like stylus events, so those events are delivered to the passive grabbers, and both the TapHandler and the ToolButton will receive the same pointer event, but TapHandler has a higher priority and when the TapHandler receives the event, the toolbutton actions become invalid because the item has changed.
This disables the TapHandler when the toolbuttons are hovered to fix the problem.