fix:failed to edit repo

[cccccarl]

return when the repo cant be found and err !=nil

Fixes #

Requirements

All new code should be covered with tests, documentation should be updated. CI should pass.

Description of the Change

The repo cant be edited

Checklist

• unit-test added (if change is algorithm)
• functional test added/updated (if change is functional)
• man page updated (if applicable)
• bash completion updated (if applicable)
• documentation updated
• author name in AUTHORS

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 66.31%. Comparing base (c9f5763) to head (0eafa62).
Report is 104 commits behind head on master.

Files	Patch %	Lines
api/repos.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1093       +/-   ##
===========================================
+ Coverage   52.11%   66.31%   +14.20%     
===========================================
  Files          73      141       +68     
  Lines       11272    15890     +4618     
===========================================
+ Hits         5874    10538     +4664     
+ Misses       4832     4603      -229     
- Partials      566      749      +183     

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[randombenj]

I don't quite get what's the problem here, I would expect that when the repo already exists with the same name that it is not renamed and this is exactly how it is implementad at the moment.
This is also the same behaviour as in the cli: https://github.com/aptly-dev/aptly/blob/master/cmd/repo_rename.go#L30