BASOP assert in Stereo fx encoder for selection test inputs

Basic info

• Encoder (fx): fe1ff93d

Bug description

BASOP asserts are hit when running the fx encoder with stereo selection test inputs

For input file `stereo-noisy_speech-p800-2-cat2-lab_d-20ms_aligned_files_concatenated_48.wav` and bitrates up to 64kbps:

Assertion failed: (0), function L_shl, file basop32.c, line 2582.

Ways to reproduce

for bitrate in 13200 24400 32000 48000 64000;
   ./IVAS_cod -stereo -max_band FB $bitrate 48 stereo-noisy_speech-p800-2-cat2-lab_d-20ms_aligned_files_concatenated_48.wav bit
end