avcodec/aacdec_fixed: Fix preparation for resampler

2nd channel makes sense only for CPE type.

Skip 2nd channel in preparation for resampler (in spectral_to _sample())
depending on block type.

Fixes fate failure with clang ftrapv.

Signed-off-by: Nedeljko Babic <nedeljko.babic@imgtec.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/aacdec_template.c

@@ -2750,7 +2750,8 @@ static void spectral_to_sample(AACContext *ac, int samples)
                     /* preparation for resampler */
                     for(j = 0; j<samples; j++){
                         che->ch[0].ret[j] = (int32_t)av_clipl_int32((int64_t)che->ch[0].ret[j]<<7)+0x8000;
-                        che->ch[1].ret[j] = (int32_t)av_clipl_int32((int64_t)che->ch[1].ret[j]<<7)+0x8000;
+                        if(type == TYPE_CPE)
+                            che->ch[1].ret[j] = (int32_t)av_clipl_int32((int64_t)che->ch[1].ret[j]<<7)+0x8000;
                     }
                 }
 #endif /* USE_FIXED */