winegstreamer: Leave pts/duration unchanged if they're not set.

dlls/winegstreamer/wm_reader.c

@@ -1660,13 +1660,20 @@ static HRESULT wm_reader_read_stream_sample(struct wm_reader *reader, struct wg_
 
     wg_parser_stream_release_buffer(stream->wg_stream);
 
+    *pts = buffer->pts;
+    *duration = buffer->duration;
+
     if (!buffer->has_pts)
+    {
         FIXME("Missing PTS.\n");
+        *pts = 0;
+    }
     if (!buffer->has_duration)
+    {
         FIXME("Missing duration.\n");
+        *duration = 0;
+    }
 
-    *pts = buffer->pts;
-    *duration = buffer->duration;
     *flags = 0;
     if (buffer->discontinuity)
         *flags |= WM_SF_DISCONTINUITY;