Handle exceptions from already-augmented segments

[jdrusso]

When continuing a simulation from a run that was in-progress, augmentation will fail because the parent segments are not loaded in WESTPA state.

This PR handles that, by ignoring the exception that's raised -- this is acceptable, because the augmentation has (hopefully) already been performed for those segments anyways.

NB: It should be explicitly checked that the segment has actually been augmented before assuming it has been. However, if it hasn't... There's not much we can do about it.

[codecov[bot]]

Codecov Report

Merging #35 (a735b15) into develop (9a20da4) will decrease coverage by 2.19%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop      #35      +/-   ##
===========================================
- Coverage    53.60%   51.40%   -2.20%     
===========================================
  Files           25       25              
  Lines         3871     3871              
===========================================
- Hits          2075     1990      -85     
- Misses        1796     1881      +85     

Impacted Files	Coverage Δ
msm_we/stratified_clustering.py	41.50% <0.00%> (-49.06%)	:arrow_down:
tests/test_msm_we.py	87.67% <0.00%> (-12.33%)	:arrow_down:
msm_we/_hamsm/_data.py	39.49% <0.00%> (-5.09%)	:arrow_down:
msm_we/msm_we.py	38.95% <0.00%> (-3.32%)	:arrow_down:
msm_we/_hamsm/_clustering.py	50.67% <0.00%> (-2.71%)	:arrow_down:

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