[Bug-apl] Listing a function shouldn't create one

[Blake McBride]

Listing a non-existent function shouldn't create a new function.  This is a
problem when you make a typo.


GNU APL:

      )CLEAR
CLEAR WS
      ∇GG[⎕]∇
    ∇
[0]   GG
    ∇
      )FNS
GG



IBM APL 2:

      )CLEAR
CLEAR WS
      ∇GG[⎕]∇
DEFN ERROR
      )FNS
      ∇GG[⎕]
DEFN ERROR
      )FNS
      ∇GG
[1]   ∇
      )FNS
GG