Explicit check against one staff-staffgroup

[Rune Zedeler]

In System_start_delimiter::print we the check to see whether a 
staff-group-symbol should suicide is

  if (ext.is_empty ()
      || (robust_scm2double (me->get_property ("collapse-height"), 0.0) 
>= ext.length ())
      || (glyph_sym == ly_symbol2scm ("bar-line")
          && non_empty_count <= 1))
    {
      me->suicide ();
      return SCM_UNSPECIFIED;
    }


Why do we have the explicit check against (glyph_sym == ly_symbol2scm 
("bar-line") && non_empty_count <= 1)?
This check ensures, that in the following snippet, the last staffgroup 
does not get a delimiter, and I see no way to circumvent it :-(


\version "2.10.25"
\layout {
  \context {
    \StaffGroup
    \override SystemStartBracket #'collapse-height = #1
  }
}
<<
\new StaffGroup <<
  \new Staff { c' }
  \new Staff { c' }
>>
\new StaffGroup <<
  \new Staff { c' }
>>
\new StaffGroup <<
  \override StaffGroup.SystemStartBracket #'style = #'bar-line
  \new Staff { c' }
  \new Staff { c' }
>>
\new StaffGroup <<
  \override StaffGroup.SystemStartBracket #'style = #'bar-line
  \new Staff { c' }
>>
>>


-Rune