patch 9.1.0387: Vim9: null value tests not sufficient

Problem:  Vim9: null value tests not sufficient
Solution: Add a more comprehensive test for null values
          (Yegappan Lakshmanan)

closes: #14701

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index 0a48b82..0754af7 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -560,7 +560,7 @@
   END
   v9.CheckSourceSuccess(lines)
 
-  # Test for using a null class with string()
+  # Test for using a null class with type() and typename()
   lines =<< trim END
     vim9script
     assert_equal(12, type(null_class))
@@ -569,30 +569,6 @@
   v9.CheckSourceSuccess(lines)
 enddef
 
-def Test_using_null_object()
-  # Test for using a null object as a value
-  var lines =<< trim END
-    vim9script
-    assert_equal(1, empty(null_object))
-  END
-  v9.CheckSourceSuccess(lines)
-
-  # Test for using a null object with string()
-  lines =<< trim END
-    vim9script
-    assert_equal('object of [unknown]', string(null_object))
-  END
-  v9.CheckSourceSuccess(lines)
-
-  # Test for using a null object with string()
-  lines =<< trim END
-    vim9script
-    assert_equal(13, type(null_object))
-    assert_equal('object<Unknown>', typename(null_object))
-  END
-  v9.CheckSourceSuccess(lines)
-enddef
-
 def Test_class_interface_wrong_end()
   var lines =<< trim END
     vim9script