empty element in 'structure'.

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

      Some of my functions use what is in practice a structure tho in
      theory I guess it's just a collection of scalars and arrays, but
      it's all copied in one go like this:
      
          set -A IN "${(@Pkv)1}" # Copy the array to IN, the working
      copy.
      
      ... anyway it's very fragile, the 'structure' must never change,
      so even when a given 'element' isn't used, it must exist.  Here's
      a slice of one such structure:
    
       body[window]="Body"           
       body[list]="body_list"     
       body[page_tops]="Btops"             
      
       Bclicks=()
       body[mouse_clicks]="Bclicks"          
      # body[mouse_clicks]="()"         
      
       body[hight]=$((Hight))       
       body[width]=$BW               
      
      ... now here's the issue: 'body[mouse_clicks]' isn't used but
      again, it must exist otherwise the 'set' command above crashes. If
      I use the rather phony:
      
     Bclicks=()
       body[mouse_clicks]="Bclicks"          
     
      ... it works fine.  But if I cut to the chase and do:
      
      body[mouse_clicks]="()"         
      
      ... it doesn't work, the 'structure' fails cuz the 'element'
      vanishes -- I think.  Purely as a question of semantics is there a
      way to do it the 'direct' way and avoid the placeholder 'Bclicks'?
      I know there's ways of hanging on to empty elements in an normal
      array and I thought the quotes  "()" would do it, but nada.  Or is
      this pushing zsh where she doesn't want to go? That is, preserving
      an entire empty array withing a pseudo structure? But again, doing
      it the 'long way' works fine.