flood fill in 3D volume can't be stopped

[acardona]

I accidentally clicked on a 1.4 GB 3D image with the flood fill tool activated, and LabKit was stuck for about 1 minute, filling the entire volume. The user error from my part was clicking to flood fill inside a 2D contour, thinking it would only fill within the visible 2D contour.

Additionally, the whole Fiji UI was stuck: as if the filling operation was running on the event dispatch thread. If so, this ought to change, and would provide the opportunity to add a "stop" button, activated while an operation runs, to cancel such long-running tasks.

At the end, I lost all my annotations for that label, because there is no undo.

Thanks for LabKit!