Bar line check is wrong with partial note and voltas

[Knute Snortum]

Hi everyone.

I think I've run into a bug.  It's hard to explain so I will post the
MWE (it's as minimal as I could make it):

%%% Start
\version "2.20.0"

rightHand = \relative c' {
  \partial 4 c4
  c4 c c

  \repeat volta 2 {
    c4 |
    c4 c c c |
  }
  \alternative {
    { c4 c c }
    { c4 c c c }
  }

  c1 |
}

\score {
  \new Staff \rightHand
  \midi {
  }
}
%%% End

The c1 at the end of the music produces a bar line check warning.  It
only happens when creating a MIDI file. It only happens when the volta
is in the middle of the measure.  It only happens when an alternate
ending doesn't contain a full measure of notes.

Any thoughts?  I really appreciate you guys.

---
Knute Snortum
(via Gmail)