Assertion error observed in stereo_dmx_evs_enc_fx from calc_poc_fx function
# Basic info
Encoder (BASOP) :
- Git SHA: 92b81e4c18fd2fa654fcf40a70aaa37ecb21bc68
# Bug description
Assertion error is observed from BASOP encoder :
```
Frames processed: 255 Assertion failed: (0), function L_shl, file basop32.c, line 2580.
```
# Ways to reproduce
```
./IVAS_cod -stereo_dmx_evs 128000 48 Clapton_Leila.wav bit
```
The call stack is :
issue