addlyrics does not work with an ossia staff

[Ansgar]

If the overall value of the second staff exhaustes the length of the part
above the following parts are spoiled:


%-----------------------
% This one works, but the added staff has only notes of value 1/2  
%-----------------------

\new Staff \relative c' 

{ e4 e e e
  
        <<      
                { e2 e  }
                \new Staff { c2  }
                \addlyrics{ Ooops! } 
        >>

{d4 d d d  }

}


%-----------------------
% Now an r is added after the c2 and that spoils the following parts
%-----------------------

\new Staff \relative c' 

{ e4 e e e
  
        <<      
                { e2 e  }
                \new Staff { c2 r }
                \addlyrics{ Ooops! } 
        >>

{d4 d d d }

}

\version "2.18.2"