fix memory allocation bug

when receiving SIGUSR1 hkd would try to allocate the new hotkey list in the old
space which could lead to errors

hkd.c

@@ -731,6 +731,7 @@ void parse_config_file (void)
 	}
 
 	hotkey_list_destroy(hotkey_list);
+	hotkey_list = NULL;
 	while (exit_state >= 0) {
 		int tmp = 0;
 		memset(block, 0, BLOCK_SIZE + 1);