Fix create repo bugs

[jolheiser]

1. Errors on repository creation were out of scope of the handling function, so Gitea showed the 500 page (because err was nil).
2. When an error occured, templateID was set to int default 0 and the JS was showing template units even though no template was chosen.

[codecov-io]

Codecov Report

Merging #9606 into master will decrease coverage by <.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #9606      +/-   ##
==========================================
- Coverage   42.17%   42.17%   -0.01%     
==========================================
  Files         578      578              
  Lines       76065    76066       +1     
==========================================
- Hits        32083    32081       -2     
- Misses      40001    40002       +1     
- Partials     3981     3983       +2

Impacted Files	Coverage Δ
routers/repo/repo.go	29.22% <66.66%> (+0.17%)	⬆️
models/unit.go	62.16% <0%> (-5.41%)	⬇️
modules/repository/repo.go	33.55% <0%> (-1.98%)	⬇️
modules/migrations/migrate.go	24.21% <0%> (-1.58%)	⬇️
modules/log/event.go	64.61% <0%> (-1.03%)	⬇️
routers/repo/view.go	38.59% <0%> (-0.88%)	⬇️
modules/migrations/gitea.go	9.03% <0%> (-0.64%)	⬇️
models/repo.go	48.08% <0%> (+0.1%)	⬆️
models/error.go	33.82% <0%> (+1.1%)	⬆️
services/pull/temp_repo.go	34.18% <0%> (+2.56%)	⬆️
... and 1 more

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[6543]

@jolheiser can you backport this to 1.10.3?

[jolheiser]

No, this bug doesn't exist in 1.10.x

[6543]

OK :)