SDK / exoplayer

This was added in https://github.com/google/ExoPlayer/commit/9609af3c23383f2fd5571662d271c3013875705d as part of a LSC.

The RequiresNonNull annotation doesn't work anymore (it doesn't
recognize the outer class member and instead tries to find
the same variable on the inner class). So instead of suppressing
the warning of the non-fulfilled precondition, we can just
check the non-nullness directly and remove the precondition.

PiperOrigin-RevId: 367593941