Validate if audioHostUrl or audioFallbackUrl is blank

[georgezy-amzn]

ℹ️ Description

• Validate if audioHostUrl or audioFallbackUrl is blank before start audio session

Issue #, if available

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
  • [ ] README update
  • [ ] CHANGELOG update
  • [ ] guides update
• [ ] This change requires a dependency update
  • [ ] Amazon Chime SDK Media
  • [ ] Other (update corresponding legal documents)

🧪 How Has This Been Tested?

describe the tests that you ran to verify your changes, any relevant details for your test configuration

Unit test coverage

• Class coverage:
• Line coverage:

Additional Manual Test

• [ ] Pause and resume remote video
• [ ] Switch local camera
• [ ] Rotate screen back and forth

📱 Screenshots, if available

provide screenshots/video record if there's a UI change in demo app

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.