Fix "Stay on Page" alert showing in empty snippet

What does this MR do?

This MR fixes that the user is prompting whether the user wants to stay on the page or leave when they refresh or click "Cancel" on a snippet page.

Now, when all fields are empty, the user will not be prompted before navigating.

Link to page: /-/snippets/new

Related to #262102 (closed)

Screenshots (strongly suggested)

Before	After
	the user will be sent to /dashboard/snippets

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team