patch 8.2.3733: Vim9: using "legacy" before range does not work

Problem:    Vim9: using "legacy" before range does not work.
Solution:   Skip over range before parsing command. (closes #9270)
diff --git a/src/testdir/test_vim9_cmd.vim b/src/testdir/test_vim9_cmd.vim
index 22b1896..ffb2bb8 100644
--- a/src/testdir/test_vim9_cmd.vim
+++ b/src/testdir/test_vim9_cmd.vim
@@ -1019,6 +1019,11 @@
   CheckScriptSuccess(['vim9script', 'silent keepjump :1d _'])
   assert_equal('', getline(1))
   bwipe!
+
+  var lines =<< trim END
+      legacy /pat/
+  END
+  CheckDefExecAndScriptFailure(lines, 'E486: Pattern not found: pat')
 enddef
 
 def Test_silent_pattern()