fix assert


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2223 35c25a1d-7b9e-4130-9fde-d3aeb78583b8
diff --git a/src/winio.c b/src/winio.c
index a4df257..54aeaf2 100644
--- a/src/winio.c
+++ b/src/winio.c
@@ -2506,7 +2506,7 @@
 		FALSE);
 
 	assert(wid > 0);
-	assert(strlen(expanded) <= wid);
+	assert(strlenpt(expanded) <= wid);
 
 	waddstr(bottomwin, expanded);
 	free(expanded);