[regression] BASOP encoder crashes in MDCT-Stereo and Multichannel

Basic info

• Encoder and Decoder (float): b63c033f
• Encoder (fixed): 64c0027b

Bug description

A BASOP assert is hit in various MDCT-Stereo bitrates with a noisy speech item in frame 2114 at ivas_stereo_mdct_core_enc_fx.c:471 in the L_sub() BASOP. This is part of the power spectrum calculation, so may be related to the recent changes done around that.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1503

./IVAS_cod_fx -q -stereo -max_band FB 64000 48 stereo-noisy_speech-p800-2-cat3-lab_d-20ms_aligned_files_concatenated_48.wav bit