Merged revisions 211232 via svnmerge from

https://origsvn.digium.com/svn/asterisk/trunk

........
  r211232 | tilghman | 2009-08-09 02:11:22 -0500 (Sun, 09 Aug 2009) | 4 lines
  
  Check for NULL frame, before dereferencing pointer.
  (closes issue #15617)
   Reported by: rain
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@211233 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_stack.c

@@ -356,7 +356,12 @@ static int local_read(struct ast_channel *chan, const char *cmd, char *data, cha
 
 	oldlist = stack_store->data;
 	AST_LIST_LOCK(oldlist);
-	frame = AST_LIST_FIRST(oldlist);
+	if (!(frame = AST_LIST_FIRST(oldlist))) {
+		/* Not within a Gosub routine */
+		AST_LIST_UNLOCK(oldlist);
+		return -1;
+	}
+
 	AST_LIST_TRAVERSE(&frame->varshead, variables, entries) {
 		if (!strcmp(data, ast_var_name(variables))) {
 			const char *tmp = pbx_builtin_getvar_helper(chan, data);