crash stereo_tca_enc_fx() for stereo encoder

Basic info

• Fixed point:
  • Encoder (fixed): ae6313fd

Bug description

When trying different files that could trigger element_mode == 3 (#1125 (closed)), stumbled across some cases where the encoder is crashing.

the encoder crashes at frame 489 with the following error :

Run-Time Check Failure 2 - Stack around the variable 'bufChanL_fx' was corrupted.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1132

IVAS_cod  -STEREO 24400 48 sh2_tv2_st.wav bit