I connected an iPad to the Mac and ran configurator as usual, updating from a back up, however it stalled out at the "Restoring Default Data" step. I tried clicking the Stop button, and now it says it's "Canceling..." but it's still not doing anything. The iPad has the apple logo and a progress bar that's at about 80%. I was able to restore one of our other iPad without trouble after I pressed start, but I can't seem to accomplish anything. Can I unplug the iPad safely and "factory reset" it or something and then update from a back up?