avcodec/apedec: fix decoding of stereo files with one channel full of silence

Signed-off-by: Paul B Mahol <onemda@gmail.com>
(cherry picked from commit 9149e9c0)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/apedec.c

@@ -1372,7 +1372,7 @@ static void ape_unpack_stereo(APEContext *ctx, int count)
     int32_t *decoded0 = ctx->decoded[0];
     int32_t *decoded1 = ctx->decoded[1];
 
-    if (ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
+    if ((ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) == APE_FRAMECODE_STEREO_SILENCE) {
         /* We are pure silence, so we're done. */
         av_log(ctx->avctx, AV_LOG_DEBUG, "pure silence stereo\n");
         return;