fix to allow empty {} values

import re

import gradio as gr

re_param_code = r"\s*([\w ]+):\s*((?:{[^}]+})|(?:[^,]+))(?:,|$)"

re_param_code = r"\s*([\w ]+):\s*((?:{[^}]*})|(?:[^,]+))(?:,|$)"

re_param = re.compile(re_param_code)

re_params = re.compile(r"^(?:" + re_param_code + "){3,}$")

re_imagesize = re.compile(r"^(\d+)x(\d+)$")