narrow: only send includepats and excludepats if they are not empty If we send an empty includepats or excludepats argument to getbundle, it's translated to `['']` on the server which causes problems because even though it's empty, bool of that value if True and we end up creating differencematcher with narrowspec.match() which results in unexpected behavior. Differential Revision: https://phab.mercurial-scm.org/D5138