用 Python 编写 Discord 机器人 - 为什么它无法设置嵌入图像?

I have a meme command that gets a URL from a subreddit and then sets it as an embed image. Here's my code:

memes = reddit.subreddit("memes")
memes_subs = []
memes_hot = memes.hot(limit = 50)

for submission in memes_hot:
  memes_subs.append(submission)


@client.command()
async def meme(ctx):
  random_sub = random.choice(memes_subs)
  name = random_sub.title
  url = random_sub.url

  em = discord.Embed(title = name, color = 0xfdcb58)
  em.set_footer(text = f"Requested by {ctx.message.author} | From r/memes")
  em.set_image(url = url)

  await ctx.send(embed = em)

有时嵌入没有图像，或者图像根本无法加载.我不确定为什么会发生这种情况，因此任何见解都将不胜感激.