grace-volta-repeat.ly regression test

[Bruce McIntyre]

Hi,

When a volta repeat includes the first bar of a piece, it is customary
to not have a ||: at the start of the music.  If, however, the music
starts with a grace-note, lilypond draws a ||:

compare

http://lilypond.org/doc/v2.3/input/regression/out-www/lily-1583180411.ly

with and without the first 

\grace {  a16[ b] }

Is this a bug or standard practice ?

Bruce.