Issue one frame boundaries when switching from dtx or CNG to MDCT (48kbps )

decoder command line:

IVAS_dec STEREO 48 bit syn

The bistream used for to recreate this issue is the following:

The problem happens both from CNG or DTX to active content as shown in the next figure. In the figure, the first spectrogram is the float synthesis, the second spectrogram is the fixed point synthesis the 3rd curve is the temporal difference between the 2 synthesis and the last one represent the bitrate (between 0 and 48 kbps) (BTW the spectrograms and the time domain signal are not aligned)

The second image is a temporal zoom to show the temporal effect on the right channel ( similar artefact are present on both channels)

Note that the second artefact happens about 1 ms after the transition