aacenc: update max_sfb when num_swb changes

This fixes out-of-bounds reads in avoid_clipping.
Reviewed-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavcodec/aacenc.c

@@ -574,6 +574,7 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
             ics->num_windows        = wi[ch].num_windows;
             ics->swb_sizes          = s->psy.bands    [ics->num_windows == 8];
             ics->num_swb            = tag == TYPE_LFE ? ics->num_swb : s->psy.num_bands[ics->num_windows == 8];
+            ics->max_sfb            = FFMIN(ics->max_sfb, ics->num_swb);
             ics->swb_offset         = wi[ch].window_type[0] == EIGHT_SHORT_SEQUENCE ?
                                         ff_swb_offset_128 [s->samplerate_index]:
                                         ff_swb_offset_1024[s->samplerate_index];