void read_config_options(avl_tree_t *config_tree, const char *prefix) {
list_node_t *node, *next;
- size_t prefix_len = strlen(prefix);
+ size_t prefix_len = prefix ? strlen(prefix) : 0;
for(node = cmdline_conf->tail; node; node = next) {
config_t *cfg = (config_t *)node->data;