UBSAN: out-of-bound error in SPAR for OSBA bitrate switching with PLC

The USAN CI tests fail due to an out-of-bound error that appears when enabling the modes with PLC in the self-test.prm in MR !1113 (merged) .

The out of bound error appears function ivas_map_prior_coeffs_quant() more specifically the error is: lib_com/ivas_spar_com_quant_util.c:181:38: runtime error: index -1 out of bounds for type 'ivas_quant_strat_t [3]'

To reproduce build with make CLANG=3 and then run either of the newly introduced tests of MR !1113 (merged) e.g.:

IVAS_cod -ism_sba 3 2 testv/stvISM1.csv testv/stvISM2.csv testv/stvISM3.csv switchPaths/sw_13k2_512k.bin 48 testv/stvOSBA_3ISM_2OA48c.wav bit

IVAS_dec -fec 10 STEREO 32 bit test.wav