apedec: set s->samples only when init_frame_decoder succeeded

Otherwise range_start_decoding is not necessarily run and thus
ctx->rc.range still 0 in range_dec_normalize leading to an infinite
loop.
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/apedec.c

@@ -1461,13 +1461,13 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
                    nblocks);
             return AVERROR_INVALIDDATA;
         }
-        s->samples = nblocks;
 
         /* Initialize the frame decoder */
         if (init_frame_decoder(s) < 0) {
             av_log(avctx, AV_LOG_ERROR, "Error reading frame header\n");
             return AVERROR_INVALIDDATA;
         }
+        s->samples = nblocks;
     }
 
     if (!s->data) {