SampleProvider throws exception for multi-channel clips

SampleProvider throws exception for multi-channel clips (4 channels or more) with the load type set to Compressed In Memory.

How to reproduce:

1. Open the attached "sample-provider-multi-channel-bug.zip" project
2. Open "Scenes > ClipPlayer"
3. Enter Play mode
4. Observe the Console window – multiple errors are logged and no sound plays:
   1. soundHandle->GetFSBData returned null.
   2. UnityException: Unable to create sample provider.
   3. Assigned scriptable generator returned an invalid instance.

Actual result: Errors are logged and no sound plays
Expected result: No errors or exceptions are logged and sound plays when entering play mode

Reproducible with: 6000.5.0a8, 6000.6.0a1
Could not test with: any version older than 6000.5.0a8 as the feature is not present before this

Reproducible on: macOS Tahoe 26.5.1
Not reproducible on: No other environments tested