Fix missing invalid time intervals

[rly]

Fix #1068

[codecov]

Codecov Report

Merging #1069 into dev will decrease coverage by 0.01%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##              dev    #1069      +/-   ##
==========================================
- Coverage   71.16%   71.15%   -0.02%     
==========================================
  Files          37       37              
  Lines        2792     2794       +2     
  Branches      554      554              
==========================================
+ Hits         1987     1988       +1     
- Misses        679      680       +1     
  Partials      126      126

Impacted Files	Coverage Δ
src/pynwb/io/base.py	28% <0%> (-0.58%)	⬇️
src/pynwb/io/file.py	75.2% <100%> (+0.2%)	⬆️

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