Revert "tspacketizer: ensure that a null pointer isn't accessed"

This reverts commit 6efd611b8c6f43f67a2f93f8445c189e24961abd.

Also this extra check won't be needed if it's fixed the race by moving
flush actions to FLUSH_STOP.

gst/mpegtsdemux/mpegtspacketizer.c

@@ -2624,7 +2624,6 @@ mpegts_packetizer_next_packet (MpegTSPacketizer2 * packetizer,
       priv->mapped =
           (guint8 *) gst_adapter_map (packetizer->adapter, priv->mapped_size);
       priv->offset = 0;
-      g_return_val_if_fail (priv->mapped, PACKET_NEED_MORE);
     }
     packet->data_start = priv->mapped + priv->offset;