patch 9.0.0811: error if :echowin is preceded by a command modifier

Problem:    Error if :echowin is preceded by a command modifier.
Solution:   Do not give an error for range when there is a modifier.
            (closes #11414)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 6c8f1f0..58e214c 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2032,6 +2032,10 @@
 def Test_echowindow_cmd()
   var local = 'local'
   echowindow 'something' local # comment
+
+  # with modifier
+  unsilent echowin 'loud'
+
   # output goes in message window
   popup_clear()
 enddef