Fix addon nil values

[qwerty287]

closes #4662

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 28.16%. Comparing base (f30fc29) to head (1ef3a12).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
server/forge/addon/args.go	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4666      +/-   ##
==========================================
- Coverage   28.17%   28.16%   -0.02%     
==========================================
  Files         398      398              
  Lines       28193    28205      +12     
==========================================
  Hits         7944     7944              
- Misses      19543    19555      +12     
  Partials      706      706              

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[woodpecker-bot]

Tearing down https://woodpecker-ci-woodpecker-pr-4666.surge.sh

[pat-s]

💚 All backports created successfully

Status	Branch	Result
✅	release/v2.8

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