Encoder crash for Stereo at 32kbps in PostShortTerm_ivas_enc_fx()
# Basic info
<!--- Add commit SHA used to reproduce -->
- Float reference:
- Encoder (float):
- Decoder (float):
- Fixed point:
- Encoder (fixed): 3d9faa50d5fce8c82a74df8924965484228a8010
- Decoder (fixed):
# Bug description
The fixed point encoder crashes with an assert:
```
Assertion failed: (0), function saturate, file basop32.c, line 510.
```



# Ways to reproduce
Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1155
<!-- Commandline or script -->
```bash
./IVAS_cod_fx -q -stereo -max_band SWB 32000 32 stereo-noisy_speech-p800-2-cat1-lab_d-20ms_aligned_files_concatenated_32.wav bit
```
If `-dtx` is added to the commandline above, the other assertion is hit in `saturate()`.
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issue