vim-patch:8.2.3657: Vim9: debug text misses one line of return statement

Problem:    Vim9: debug text misses one line of return statement.
Solution:   Add a line when not at a debug instruction. (closes vim/vim#9137)

112bed0cbe

Vim9 test "Test_Debugger_break_at_return()" commented out
to avoid unexpected side-effects even if all other tests pass.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

test/old/testdir/test_debugger.vim

@@ -436,6 +436,29 @@ func Test_Debugger_breakadd_expr()
   call StopVimInTerminal(buf)
 endfunc
 
+" def Test_Debugger_break_at_return()
+"   var lines =<< trim END
+"       vim9script
+"       def g:GetNum(): number
+"         return 1
+"           + 2
+"           + 3
+"       enddef
+"       breakadd func GetNum
+"   END
+"   writefile(lines, 'Xtest.vim')
+"
+"   # Start Vim in a terminal
+"   var buf = RunVimInTerminal('-S Xtest.vim', {wait_for_ruler: 0})
+"   call TermWait(buf)
+"
+"   RunDbgCmd(buf, ':call GetNum()',
+"      ['line 1: return 1  + 2  + 3'], {match: 'pattern'})
+"
+"   call StopVimInTerminal(buf)
+"   call delete('Xtest.vim')
+" enddef
+
 func Test_Backtrace_Through_Source()
   CheckRunVimInTerminal
   CheckCWD