Assert in stereo_dft_generate_comfort_noise_fx() for stereo bitstream with dtx and bit rate switching
# Basic info
<!--- Add commit SHA used to reproduce -->
- Float reference:
- Encoder (float):
- Decoder (float):
- Fixed point:
- Encoder (fixed):
- Decoder (fixed): 8e8b913a7a845137424deca5bfaad1299be3f955
# Bug description
While checking for possible issues related to extract_l() , I stumble on this assert() which happens with and without the activation of #2493 related switches.
{width=900 height=490}
# Ways to reproduce
[bit.flt](/uploads/1d7be42edf59472ea939ac4278dc6b9f/bit.flt)
Using the attached bitstream and the following command line :
```bash
IVAS_dec STEREO 48 bit.flt syn
```
<!--- Below are labels that will be added but are not shown in description. This is a template to help fill them.
Add further information to the first row and remove and add labels as necessary. -->
issue