avformat/avidec: Add flac to the dshow_block_align exception list

Fixes Ticket4758
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/avidec.c

@@ -872,8 +872,9 @@ static int avi_read_header(AVFormatContext *s)
                         st->codec->codec_id    = AV_CODEC_ID_ADPCM_IMA_AMV;
                         ast->dshow_block_align = 0;
                     }
-                    if (st->codec->codec_id == AV_CODEC_ID_AAC && ast->dshow_block_align <= 4 && ast->dshow_block_align ||
-                        st->codec->codec_id == AV_CODEC_ID_MP2 && ast->dshow_block_align <= 4 && ast->dshow_block_align) {
+                    if (st->codec->codec_id == AV_CODEC_ID_AAC  && ast->dshow_block_align <= 4 && ast->dshow_block_align ||
+                        st->codec->codec_id == AV_CODEC_ID_FLAC && ast->dshow_block_align <= 4 && ast->dshow_block_align ||
+                        st->codec->codec_id == AV_CODEC_ID_MP2  && ast->dshow_block_align <= 4 && ast->dshow_block_align) {
                         av_log(s, AV_LOG_DEBUG, "overriding invalid dshow_block_align of %d\n", ast->dshow_block_align);
                         ast->dshow_block_align = 0;
                     }