Found naked nipple under w/w reservoir...

[NHAndy]

1996 c280 sport,
I've searched these archives and not found an answer.
I removed the windshield washer reservoir and found a switch with an electrical connector. One vacuum line on the suction end is connected but there is a naked nipple that sticks straight up at that end also. The connection at the other end goes to the intake manifold.
My question is what is suppose to be connected to that naked nipple? and is this throwing a code p0441 CEL?
There are no disconnected vac lines readily apparent in the area.
Thanks.