L2SS-340: Ignore packets without timestamp, log reason why we stopped processing.

devices/statistics_writer/hdf5_writer.py

@@ -65,6 +65,12 @@ class hdf5_writer:
         # grab the timestamp
         statistics_timestamp = statistics_packet.timestamp()
 
+        # ignore packets with no timestamp, as they indicate FPGA processing was disabled
+        # and are useless anyway.
+        if statistics_packet.block_serial_number == 0:
+            logger.warning(f"Received statistics with no timestamp. Packet dropped.")
+            return
+
         # check if te statistics timestamp is unexpectedly older than the current one
         if statistics_timestamp < self.current_timestamp:
             logger.warning(f"Received statistics with earlier timestamp than is currently being processed ({statistics_timestamp}). Packet dropped.")