Fix webcam when streaming=True

[hannahblair]

Description

#6766 broke the Webcam when streaming is true due to a !value check when rendering <Webcam />. This PR fixes that logic and adds a story test.

Closes: #6858

🎯 PRs Should Target Issues

Before your create a PR, please check to see if there is an existing issue for this change. If not, please create an issue before you create this PR, unless the fix is very small.

Not adhering to this guideline will result in the PR being closed.

Tests

1. PRs will only be merged if tests pass on CI. To run the tests locally, please set up your Gradio environment locally and run the tests: bash scripts/run_all_tests.sh

2. You may need to run the linters: bash scripts/format_backend.sh and bash scripts/format_frontend.sh

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	ready!	Website preview
	Storybook	ready!	Storybook preview
	Visual tests	all good!	Build review
🦄	Changes	detected!	Details

---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/994c01558bb2c6c407c8c824c7493306e77b2618/gradio-4.11.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@994c01558bb2c6c407c8c824c7493306e77b2618#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/image	patch
gradio	patch

• Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Fix webcam when streaming=True

Maintainers or the PR author can modify the PR title to modify this entry.

Something isn't right?

• Maintainers can change the version label to modify the version bump.
• If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can update the changelog file directly.

[abidlabs]

LGTM, thanks for adding the story @hannahblair!