The last used fill attributes ase used. Pen with shape -usually a filled path; pen without a shape -usually a path with no fill but stroke. Confusing that you got a filled path but the behave is somewhat on purpose. Not a bug. Oh right Yeah I actually just fixed the problem. Thanks..Its definitely ...

When the pen tool shape is set to none it doesnt behave as expected.

You should get a line, but what happens is you get a shape, as in the line you just drew connects its ends together.

See pictures for explanation.

http://imgur.com/qZgLIcB