Fix some more error cases found by Go Fuzz

[bep]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.16667% with 10 lines in your changes missing coverage. Please review.

Project coverage is 79.89%. Comparing base (c3bc947) to head (33af97d).

Files	Patch %	Lines
helpers.go	71.42%	5 Missing and 1 partial ⚠️
imagemeta.go	81.81%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #25      +/-   ##
==========================================
- Coverage   79.92%   79.89%   -0.03%     
==========================================
  Files          14       14              
  Lines        1250     1283      +33     
==========================================
+ Hits          999     1025      +26     
- Misses        175      181       +6     
- Partials       76       77       +1     

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