Assert in ivas_cpe_enc_fx for OMASA rate switching input (new STV)
# Basic info
<!--- Add commit SHA used to reproduce -->
- Fixed point:
- Encoder (fixed): 028d6837bd6d57fb08f26f92f6678327f74eb3c0
# Bug description
See job here https://forge.3gpp.org/rep/sa4/audio/ivas-basop/-/jobs/621112
There is an assert with new OMASA STV test vector on the BASOP encoder. This is rate switching and the switch happening in the crashing frame 938 is from 64 kbps to 13.2 kbps at least based on the encoder config structure. Element mode seems to be `IVAS_CPE_DFT` and last element mode was `IVAS_CPE_MDCT`.
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# Ways to reproduce
<!-- Commandline or script -->
```bash
./IVAS_cod -ism_masa 4 2 NULL /scripts/testv/stv20sOMASA_4ISM2TC_ISM2.csv /scripts/testv/stv20sOMASA_4ISM2TC_ISM3.csv /scripts/testv/stv20sOMASA_4ISM2TC_ISM4.csv /scripts/testv/stv20sOMASA_4ISM2TC.met /scripts/switchPaths/sw_13k2_512k_2fr_start_80k_omasatechs_4ism.bin 48 /scripts/testv/stv20sOMASA_4ISM2TC.wav debug.bit
```
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issue