crash stereo_tca_enc_fx() for stereo encoder
# Basic info
<!--- Add commit SHA used to reproduce -->
- Fixed point:
- Encoder (fixed): ae6313fd
# Bug description
When trying different files that could trigger element_mode == 3 (#1125), 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
```bash
IVAS_cod -STEREO 24400 48 sh2_tv2_st.wav bit
```
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issue