patch 8.2.1365: Vim9: no error for missing white space around operator

Problem:    Vim9: no error for missing white space around operator.
Solution:   Check for white space. (closes #6618)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index f3fc4c7..d024836 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1270,7 +1270,7 @@
 def TreeWalk(dir: string): list<any>
   return readdir(dir)->map({_, val ->
             fnamemodify(dir .. '/' .. val, ':p')->isdirectory()
-               ? {val : TreeWalk(dir .. '/' .. val)}
+               ? {val: TreeWalk(dir .. '/' .. val)}
                : val
              })
 enddef