Melody_engraver and tied notes

Hello everyone,

Melody_engraver readily sets different stem directions either side of a 
tie. I don’t think it should do that.

%%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.25.2"

\layout {
   \context {
     \Voice
     \remove Note_heads_engraver
     \consists Completion_heads_engraver
     \consists Melody_engraver
   }
}
\relative {
   d''2. b4~ 4 g2 b2 d2.
}
%%%%%%%%%%%%%%%%%%%%%%%%%%

Technically, not a minimal example, since Completion_heads_engraver 
isn’t really related. I just figured I include it to be safe, in case 
behaviour differs in any way with regard to potential fixes.

Best, Simon