Error processing .nm4 and .nmea files

[tsuzzy]

When using the function aisdb.database.decode_msgs() to decode and process .nm4 and .nmea files, the following message is prompted:

error processing path/to/filename.nm4, skipping checksum...

This results in an empty table being created in the SQLite database.

The issue can be reproduced with the following code,:

import aisdb

filepath = ['./sample_data.nm4']

with aisdb.DBConn(dbpath = 'sample.db') as dbconn:
    aisdb.decode_msgs(filepaths=filepath, dbconn=dbconn, source='TESTING')

Content in sample_data.nm4 is:

\s:41925,c:1635731906,t:1635731966*63\!AIVDM,1,1,,,11mg=5@000<Oe=Cbv:E@08L`00Ra,0*41
\s:41925,c:1635731906,t:1635731966*63\!AIVDM,1,1,,,15Utl40P0:<2TeiUEfmbk?vd08=T,0*78

Expected the file should be processed and data should be populated in the database.

Actual output:

generating file checksums...
checking file dates...
creating tables and dropping table indexes...
Memory: 21.92GB remaining.  CPUs: 12.  Average file size: 0.00MB  Spawning 4 workers
processing ./sample_data.nm4
saving checksums...
error processing ./sample_data.nm4, skipping checksum...
cleaning temporary data...

As observed, the message indicates a failure in processing the file, leading to the checksum being skipped and an empty table in the database.
Running the test script test_002_decode.py produces a similar output. However, the test passes because this failure does not raise any errors.

Environment:

• OS: Ubuntu 22.04.4 LTS
• Python version: 3.10.12
• AISdb version: 1.7.3

[gabrielspadon]

Related to #78 , please address this issue as well.

[gabrielspadon]

Also related to #85 , please address this issue as well.