MDCT-Stereo concealment - discontinuity introduced by PLC

Basic info

• Encoder (float): d9fdb374
• Decoder: 01446363

Bug description

The fx decoder can introduce discontinnuities in the signal during PLC in MDCT-Stereo, see here at 4.04s:

This particular one is not very audible which is most likely due to the signal content (very "clicky" electronic kick drum). The underlying problem should be fixed, however.

Ways to reproduce

./IVAS_dec_fx stereo 48 stereo-mixed-music--ap03a3s02--48000.192 stereo-mixed-music--ap03a3s02--48000.clean.dec.fx.wav
./IVAS_dec_flt_ref stereo 48 stereo-mixed-music--ap03a3s02--48000.192 stereo-mixed-music--ap03a3s02--48000.clean.dec.flt.wav

Bitstream will be shared separately as usual.

(Clear steps or refer to a failing automated test, e.g. with a pipeline link)