avcodec/dca: fix sync word search error condition

This didn't actually check if sync word was found and always errored out
with "-err_detect explode" option enabled.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/dca_core.c

@@ -1844,8 +1844,9 @@ static int parse_optional_info(DCACoreDecoder *s)
                 }
             }
 
-            if (s->avctx->err_recognition & AV_EF_EXPLODE) {
+            if (!s->xch_pos) {
                 av_log(s->avctx, AV_LOG_ERROR, "XCH sync word not found\n");
+                if (s->avctx->err_recognition & AV_EF_EXPLODE)
                     return AVERROR_INVALIDDATA;
             }
             break;
@@ -1866,8 +1867,9 @@ static int parse_optional_info(DCACoreDecoder *s)
                 }
             }
 
-            if (s->avctx->err_recognition & AV_EF_EXPLODE) {
+            if (!s->x96_pos) {
                 av_log(s->avctx, AV_LOG_ERROR, "X96 sync word not found\n");
+                if (s->avctx->err_recognition & AV_EF_EXPLODE)
                     return AVERROR_INVALIDDATA;
             }
             break;
@@ -1891,8 +1893,9 @@ static int parse_optional_info(DCACoreDecoder *s)
                 }
             }
 
-            if (s->avctx->err_recognition & AV_EF_EXPLODE) {
+            if (!s->xxch_pos) {
                 av_log(s->avctx, AV_LOG_ERROR, "XXCH sync word not found\n");
+                if (s->avctx->err_recognition & AV_EF_EXPLODE)
                     return AVERROR_INVALIDDATA;
             }
             break;