patch 8.2.4809: various things no6 properly tested

Problem:    Various things no6 properly tested.
Solution:   Add various test cases. (Yegappan Lakshmanan, closes #10259)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 02946a3..74159ca 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -3780,6 +3780,16 @@
   v9.CheckDefAndScriptFailure(lines, ['E476:', 'E492:'])
 
   lines =<< trim END
+      :k a
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E1100:')
+
+  lines =<< trim END
+      :1k a
+  END
+  v9.CheckDefAndScriptFailure(lines, 'E481:')
+
+  lines =<< trim END
     t
   END
   v9.CheckDefAndScriptFailure(lines, 'E1100:')