patch 8.2.4530: making comparison with null work changes legacy behavior

Problem:    Making comparison with null work changes legacy behavior.
Solution:   Only use the better comparison in Vim9 script. (closes #9910)
diff --git a/src/typval.c b/src/typval.c
index e89ba9e..53512c6 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -1381,7 +1381,7 @@
 }
 
 /*
- * Compare v:null/v:none with another type.  Return TRUE if the value is NULL.
+ * Compare v:null with another type.  Return TRUE if the value is NULL.
  */
     int
 typval_compare_null(typval_T *tv1, typval_T *tv2)
@@ -1417,6 +1417,9 @@
 	    default: break;
 	}
     }
+    if (!in_vim9script())
+	return FALSE;  // backwards compatible
+
     semsg(_(e_cannot_compare_str_with_str),
 			 vartype_name(tv1->v_type), vartype_name(tv2->v_type));
     return MAYBE;