Tracker add CRC check and TRB error and module error detection fix

• Fixes a tiny typo so that TRB and module errors are detected.
• This implements the Fletcher checksum check in TrackerDataFragment. Note: A mismatched checksum does not throw an exception, but is checked in valid(). TRB and module errors still do throw an exception.
• modified eventDump to guard against exceptions thrown, which are now more likely due to module/trb error fix.