fix memory leak due to not freeing the channel's string fields in

ast_channel_destroy() (issue #6746)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@13628 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channel.c

@@ -1006,6 +1006,7 @@ void ast_channel_free(struct ast_channel *chan)
 	while ((vardata = AST_LIST_REMOVE_HEAD(headp, entries)))
 		ast_var_delete(vardata);
 
+	ast_string_field_free_all(chan);
 	free(chan);
 	AST_LIST_UNLOCK(&channels);