Catch TypeErrors that arise writing StateVector objects

[alurban]

This PR applies a band-aid to an error I'm seeing in production, in which gwsumm.archive._write_data fails on writing StateVector objects because of byte representation.

cc @duncanmmacleod

[codecov]

Codecov Report

Merging #326 (9eeaba5) into master (8a6790e) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #326   +/-   ##
=======================================
  Coverage   50.47%   50.47%           
=======================================
  Files          60       60           
  Lines        8636     8636           
=======================================
  Hits         4359     4359           
  Misses       4277     4277           

Flag	Coverage Δ
Linux	50.47% <0.00%> (ø)
python36	49.67% <0.00%> (ø)
python37	49.67% <0.00%> (ø)
python38	50.47% <0.00%> (ø)
python39	50.47% <0.00%> (ø)

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Impacted Files	Coverage Δ
gwsumm/archive.py	76.97% <0.00%> (ø)

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