Fix bugs of Stable Diffusion

[CaffreyR]

What does this PR do?

Fix bugs of Stable Diffusion mentioned in #6201 , might could merge together with #6135

Fixes#6201

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@patrickvonplaten and @sayakpaul
Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

[sayakpaul]

Cc: @williamberman here.

[patrickvonplaten]

this is not correct. Even if prompt_embeds is not None self.encode_prompt should be called (see how the prompt_embeds variable is passed to the function)

[CaffreyR]

Then please see https://github.com/huggingface/diffusers/blob/main/examples/dreambooth/train_dreambooth_lora.py#L1239,
when prompt_embeds is given, the model does not give prompt to the pipeline.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the contributing guidelines are likely to be ignored.