[OpenSmalltalk/opensmalltalk-vm] 6a7f91: Fix issue #472 (#473)

 
  Branch: refs/heads/Cog
  Home:   https://github.com/OpenSmalltalk/opensmalltalk-vm
  Commit: 6a7f9170f22221bc697a30844591a0ecf299bf3d
      https://github.com/OpenSmalltalk/opensmalltalk-vm/commit/6a7f9170f22221bc697a30844591a0ecf299bf3d
  Author: Nicolas Cellier <[hidden email]>
  Date:   2020-01-24 (Fri, 24 Jan 2020)

  Changed paths:
    M platforms/Cross/plugins/Squeak3D/b3dInit.c

  Log Message:
  -----------
  Fix issue #472 (#473)

when `i == j`, there is nothing to sort.
If we call this for the first time, there is no stack allocated by `INIT(0)`, but stack is accessed nonetheless thru `PUSH(i,j)`.
The best thing todo IMO is to return early.