This is a fix for bug T53529.
I'm fairly new to the Blender project, so I'm not sure if this is 100% correct or the best way to fix this. Feel free to leave any feedback.
The problem was just that there was no loop associated with the edge where the code assumed there would be one. This fix adds logic for the special case where you are ripping one vertex along an edge that doesn't have a face associated with it.