Fix issue #472 (#473)
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.
timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,OpenSmalltalk/vm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm,timfel/squeakvm,timfel/squeakvm,OpenSmalltalk/vm,timfel/squeakvm