patch 8.2.1531: Vim9: test still fails on MS-Windows

Problem:    Vim9: test still fails on MS-Windows.
Solution:   When skipping expect function to be NULL.

Author: brammool

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1531,
 /**/
     1530,
 /**/

src/vim9compile.c

@@ -4271,7 +4271,7 @@ compile_nested_function(exarg_T *eap, cctx_T *cctx)
     ufunc = def_function(eap, lambda_name);
 
     if (ufunc == NULL)
-	return NULL;
+	return eap->skip ? (char_u *)"" : NULL;
     if (ufunc->uf_def_status == UF_TO_BE_COMPILED
 	    && compile_def_function(ufunc, TRUE, cctx) == FAIL)
 	return NULL;