IGF Stereo TCX noise filling substitution done on the wrong spectra

Basic info

Bug description

The IGF decoder in the copy up of source regions replaces lines generated by the TCX core coder noisefilling with newly generated random noise. In the IGF stereo encoder this replacement is done on the wrong source spectra in case of frames with no whitening singalled for IGF.

Ways to reproduce

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