Renderer crash with assert for OMASA to MONO (renderBufferChannelLerp_fx)
# Basic info
<!--- Add commit SHA used to reproduce -->
- Float reference:
- Renderer (float): f40fa467
- Fixed point:
- Renderer (fixed): ced61be13
# Bug description
Rendering an OMASA item defined using the META input crashes with an assert error
```
IVAS_rend: lib_com/basop32.c:1742: L_sub: Assertion `0' failed.
```
Stack:
```
L_sub basop32.c:1742
L_sub basop32.c:1742
renderBufferChannelLerp_fx lib_rend_fx.c:4633
renderIsmToMc lib_rend_fx.c:5402
renderInputIsm lib_rend_fx.c:5624
renderActiveInputsIsm lib_rend_fx.c:5691
getSamplesInternal lib_rend_fx.c:7343
IVAS_REND_GetSamples lib_rend_fx.c:7384
main renderer.c:1491
```
# Ways to reproduce
<!-- Commandline or script -->
```bash
IVAS_rend -q -if meta -i scripts/testv/stvOMASA_3ISM_2MASA2TC32c.txt -fs 32 -of MONO -o 0193_stvOMASA_3ISM_2MASA2TC32c.wav_MONO.wav
```
The file `stvOMASA_3ISM_2MASA2TC32c.txt` has the content
```
stvOMASA_3ISM_2MASA2TC32c.wav
4
ISM
1
stvOMASA_3ISM_2MASA1TC48c_ISM1.csv
ISM
2
stvOMASA_3ISM_2MASA1TC48c_ISM2.csv
ISM
3
stvOMASA_3ISM_2MASA1TC48c_ISM3.csv
MASA
4
2
stvOMASA_3ISM_2MASA1TC48c.met
```
and should be placed where STVs are (`scripts/testv/`).
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issue