Decoder crash for MC51 at 128/256/384/512kbps FER in LFE PLC

The fixed point decoder crashes in basop32.c:1877 with an assert for multiple bitrates.

Frames processed:       255     Assertion failed: (0), function L_sub, file basop32.c, line 1877.

Steps to reproduce:

./IVAS_cod_flt_ref -mc 5_1 -max_band FB 512000 48 experiments/basop-verification/MC-5_1/proc_input/bm2aa1s03.wav out/mc-5_1--bm2aa1s03--512000.192
eid-xor -vbr -fer out/mc-5_1--bm2aa1s03--512000.192 error_patterns/mc-5_1--bm2aa1s03--512000_ep.192 out/mc-5_1--bm2aa1s03--512000.fer.192
./IVAS_dec_fx 5_1 48 out/mc-5_1--bm2aa1s03--512000.fer.192 out/mc-5_1--bm2aa1s03--512000.fer.dec.fx.wav

This crash also occurs for the bitstreams listed (the bitrate and item name can be replaced in the commands above):

• mc-5_1--bm2aa1s03--128000.fer.192
• mc-5_1--am2ba1s03--128000.fer.192
• mc-5_1--am2ba1s03--256000.fer.192
• mc-5_1--am2ba1s12--384000.fer.192
• mc-5_1--am2ba1s03--512000.fer.192

Float reference SHA (_flt_ref): d9fdb374

FX binary SHA (_fx): 2470528b

Error pattern file(s):

• mc-5_1--bm2aa1s03--512000_ep.192
• mc-5_1--bm2aa1s03--128000_ep.192
• mc-5_1--am2ba1s03--128000_ep.192
• mc-5_1--am2ba1s03--256000_ep.192
• mc-5_1--am2ba1s12--384000_ep.192
• mc-5_1--am2ba1s03--512000_ep.192

Bitstream(s) can be shared upon request.