patch 8.2.4487: Vim9: cannot compare with v:null

Problem:    Vim9: cannot compare with v:null.
Solution:   Allow comparing anything with v:null. (closes #9866)
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 91464a7..028e1a7 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -1846,6 +1846,8 @@
         ['true != isFalse', 'COMPAREBOOL !='],
         ['v:none == isNull', 'COMPARESPECIAL =='],
         ['v:none != isNull', 'COMPARESPECIAL !='],
+        ['"text" == isNull', 'COMPARENULL =='],
+        ['"text" != isNull', 'COMPARENULL !='],
 
         ['111 == aNumber', 'COMPARENR =='],
         ['111 != aNumber', 'COMPARENR !='],