libview: Reset `pressed_button` when starting Drag and Drop
If view->pressed_button is left set, when the Drag and Drop operation completes, Evince will act as if it is still in a selection event.
Fixes #754 (closed)
If view->pressed_button is left set, when the Drag and Drop operation completes, Evince will act as if it is still in a selection event.
Fixes #754 (closed)