SoftXAAC: Removed redundant null checks for inHeader

inHeader is always guaranteed to be non Null as it reads from
inQueue which is non empty

Bug: 80428530
Test: CTS android.media.cts.DecoderTest{AacDrc,XheAac}
Change-Id: I5bb7d119c211025c88c7f685cb6e46555467cfb8
1 file changed