Short description of error
meta-andoctro on IRC asked me to help find out what is wrong with the Mesh: Extra Tools Multi Face Extrude / Add Armature tool. I have managed to confuse myself.
Exact steps for others to reproduce the error
start with the default cube.
go to the addons tab in the Tool region and chose Multi Face Extrude from the Multi Extrude Plus panel
Without doing anything else, click the Add Armature button.
The operator will fail with a "Select a face or a vertex where the chain should end..." error message.
According to meta-andoctro this workflow used to work in the past. I'll let him provide more detail.