Decoder crash for ParamUpmix MC 7.1+4 at 160kbps decoding to mono at 16/32kHz in ivas_ls_setup_conversion_process_mdct_fx()

Basic info

• Float reference:
  • Encoder (float): db364042
  • Decoder (float): db364042
• Fixed point:
  • Decoder (fixed): c7a85855

Bug description

The fixed point decoder crashes with an assert:

Assertion failed: (0), function L_add, file basop32.c, line 1661.

Ways to reproduce

Box folder: ...\Box_EXTERNAL_IVAS_BASOP_VERIFICATION\issues\issue-1798

./IVAS_dec mono 32 bit out.wav

The assert occurs only for mono output at 16/32kHz. 48kHz output does not crash. Likely related to #1797 (closed).