Don't show source select dialog when media player Unavailable.

[pszafer]

Proposed change

Now select_source is disabled only in 'off' state.
It should be disabled for unavailable and unknown as well.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

None

Additional information

Whole change is just checking !["off", "unavailable"].includes(stateObj.state)

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io