error on SystemStartDelimeterHierarchy snippet 2.19.82

[Juan Cristóbal Cerrillo]

Hello,

This snippet (Notation Reference 1.6.1) works fine on 2.18.2-1 but is incorrect on 2.19.82-1 (the SystemStartSquare on staff b vanishes).

\new StaffGroup
\relative c'' <<
  \set StaffGroup.systemStartDelimiterHierarchy
    = #'(SystemStartSquare (SystemStartBrace (SystemStartBracket a
                             (SystemStartSquare b)  ) c ) d)
  \new Staff { c1 }
  \new Staff { c1 }
  \new Staff { c1 }
  \new Staff { c1 }
  \new Staff { c1 }
>>

Best,

jc