Add NONBE_1233_HQ_CLASSIFIER_DIV_BY_ZERO to address potential division by zero in hq_classifier

The hf_spectrum_sparseness calculation fails when the input high band spectrum is all zero. This MR identifies this situation by checking if the maximum absolute value Amax is zero. For a flat spectrum the crest is 0, so the calculation is skipped in this case.

The change looks larger since the existing code was put in an else branch and indented one step.