fixed BrowserType.launch: Target page, context or browser has been cl…

[Sanjaypranav]

…osed" crawl4AI

Summary

Please include a summary of the change and/or which issues are fixed.

eg: Fixes #123 (Tag GitHub issue numbers in this format, so it automatically links the issues with your PR)

List of files changed and why

eg: quickstart.py - To update the example as per new changes

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have added/updated unit tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes