Give an error message when returning due to an unallocated channel element

Patch by Alex Converse ( alex converse gmail com )

Originally committed as revision 17181 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/aac.c

@@ -1576,7 +1576,10 @@ static int aac_decode_frame(AVCodecContext * avccontext, void * data, int * data
         }
         if(elem_type < TYPE_DSE) {
             if(!ac->che[elem_type][elem_id])
+            {
+                av_log(ac->avccontext, AV_LOG_ERROR, "channel element %d.%d is not allocated\n", elem_type, elem_id);
                 return -1;
+            }
         }
 
         switch (elem_type) {