Stop not working properly

[tavmem]

This issue was identified while investigating issue 454 ( _f )

in k2.8:

  tst:{[] a:1; \ b:2; a+b}
  \b s                           /set stop
  tst[]
stop
{[] a:1; \ b:2; a+b}             /stop line shown
         ^
>  b                             /tracked value available
2
>  _f                            /complete function viewable using _f
{[] a:1; \ b:2; a+b}

in Kona:

  tst: {[] a:1; \ b:2; a+b}
  \b s                           /set stop
  tst[]
stop                             /stop line NOT shown
>  b
value error                      /tracked value NOT available
b
^
>  _f                            /complete function NOT viewable using _f
>