Noise-burst artifacts before transients for McMASA 64kbps

This was detected with one of the characterization items. For the mid-channel there are some noise bursts happening for some transients causing and ugly audible artifact. These happen for example at frames 96 and 119 as can be seen below:

Coded with 64 kbps

Original:

To reproduce:

./IVAS_cod -mc 7_1_4 64000 48 dm09a1s04.wav dm09a1s04.ivas.192
./IVAS_dec 7_1_4 48 dm09a1s04.ivas.192 dm09a1s04.ivas.dec.wav

Item can has been uploaded here: /EXTERNAL_IVAS_CHAR_MC/Issues/ivas-codec-issue-1408