Fix memory leak when reading group input.

[marlam]

Since this occurs in a potentially endless loop, a malicious user could cause resource exhaustion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.42%. Comparing base (e5a0b54) to head (268a08e).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #101      +/-   ##
==========================================
+ Coverage   71.02%   71.42%   +0.40%     
==========================================
  Files           6        6              
  Lines         283      287       +4     
  Branches       44       44              
==========================================
+ Hits          201      205       +4     
  Misses         71       71              
  Partials       11       11              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[mrvanes]

Good catch!