Decoder crash for stereo at 80kbps JBM decoding to Mono in get_scaling_quality_fx()
# Basic info
<!--- Add commit SHA used to reproduce -->
- Float reference:
- Encoder (float): f2eb9e0831ece72ec66a0c07e62d1f3302e2a910
- Decoder (float):
- Fixed point:
- Encoder (fixed):
- Decoder (fixed): e4d04686dee5389b2a45b90c65ab869353f58c2f
# Bug description
The fixed point decoder crashes with an assert:
```
Assertion failed: (0), function L_add, file basop32.c, line 1661.
```
{width=415 height=227}
# Ways to reproduce
Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1373
<!-- Commandline or script -->
```bash
./IVAS_cod_flt_ref -q -stereo -max_band FB 80000 48 dp03a1s05_48.wav bit
networkSimulator_g192 ./scripts/dly_error_profiles/dly_error_profile_2.dat bit bit_sim netsim.trace 1 0
./IVAS_dec -voip mono 16 bit_sim out.wav
```
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issue