Add missing goto and fix tests

[jeromekelleher]

Closes #160

This was a bug, but a vanishingly unlikely one to ever actually occur because it would have to happen when closing a read-only file.

[codecov]

Codecov Report

Merging #164 (ec69b05) into main (19185bd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #164   +/-   ##
=======================================
  Coverage   93.66%   93.66%           
=======================================
  Files          14       14           
  Lines        1294     1294           
  Branches      192      192           
=======================================
  Hits         1212     1212           
  Misses         50       50           
  Partials       32       32           

Flag	Coverage Δ
C	93.66% <ø> (ø)
python	93.66% <ø> (ø)

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[benjeffery]

LGTM