Subject: Prevent segfault for formUpdateBuffer
Author: Tatsuya Kinoshita <tats@debian.org>
Bug-Debian: https://github.com/tats/w3m/issues/22 [CVE-2016-9440]
Origin: https://anonscm.debian.org/cgit/collab-maint/w3m.git/commit/?id=4a8d16fc8d08206dd7142435054ee38ff41805b7

diff --git a/form.c b/form.c
index 779ba2f..20b7310 100644
--- a/form.c
+++ b/form.c
@@ -461,6 +461,8 @@ formUpdateBuffer(Anchor *a, Buffer *buf, FormItemList *form)
 #endif				/* MENU_SELECT */
 	    p = form->value->ptr;
 	l = buf->currentLine;
+	if (!l)
+	    break;
 	if (form->type == FORM_TEXTAREA) {
 	    int n = a->y - buf->currentLine->linenumber;
 	    if (n > 0)