avformat/mxfdec: drop invalid index table segments when sorting them

This way if an index table segment is present multiple times, we can always use
the proper one instead of the invalid one.

Fixes seeking in the sample of ticket #5671.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavformat/mxfdec.c

@@ -1348,9 +1348,22 @@ static int mxf_get_sorted_table_segments(MXFContext *mxf, int *nb_sorted_segment
         return AVERROR(ENOMEM);
     }
 
-    for (i = j = 0; i < mxf->metadata_sets_count; i++)
-        if (mxf->metadata_sets[i]->type == IndexTableSegment)
-            unsorted_segments[j++] = (MXFIndexTableSegment*)mxf->metadata_sets[i];
+    for (i = nb_segments = 0; i < mxf->metadata_sets_count; i++) {
+        if (mxf->metadata_sets[i]->type == IndexTableSegment) {
+            MXFIndexTableSegment *s = (MXFIndexTableSegment*)mxf->metadata_sets[i];
+            if (s->edit_unit_byte_count || s->nb_index_entries)
+                unsorted_segments[nb_segments++] = s;
+            else
+                av_log(mxf->fc, AV_LOG_WARNING, "IndexSID %i segment at %"PRId64" missing EditUnitByteCount and IndexEntryArray\n",
+                       s->index_sid, s->index_start_position);
+        }
+    }
+
+    if (!nb_segments) {
+        av_freep(sorted_segments);
+        av_free(unsorted_segments);
+        return AVERROR_INVALIDDATA;
+    }
 
     *nb_sorted_segments = 0;
 
@@ -1482,7 +1495,7 @@ static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_t
 
             if (s->edit_unit_byte_count)
                 offset_temp += s->edit_unit_byte_count * index;
-            else if (s->nb_index_entries) {
+            else {
                 if (s->nb_index_entries == 2 * s->index_duration + 1)
                     index *= 2;     /* Avid index */
 
@@ -1493,10 +1506,6 @@ static int mxf_edit_unit_absolute_offset(MXFContext *mxf, MXFIndexTable *index_t
                 }
 
                 offset_temp = s->stream_offset_entries[index];
-            } else {
-                av_log(mxf->fc, AV_LOG_ERROR, "IndexSID %i segment at %"PRId64" missing EditUnitByteCount and IndexEntryArray\n",
-                       index_table->index_sid, s->index_start_position);
-                return AVERROR_INVALIDDATA;
             }
 
             if (edit_unit_out)