Fix bug when displaying git user avatar in commits list (go-gitea#35003)

A quick fix for go-gitea#34991 

`ValidateCommitsWithEmails` will create a fake user for a git commit
user with a related Gitea user. The UI should not display a link for
such users.

Author: lunny

templates/repo/commits_list.tmpl

@@ -16,7 +16,7 @@
 					<td class="author">
 						<div class="tw-flex">
 							{{$userName := .Author.Name}}
-							{{if .User}}
+							{{if and .User (gt .User.ID 0)}} /* User with id == 0 is a fake user from git author */
 								{{if and .User.FullName DefaultShowFullName}}
 									{{$userName = .User.FullName}}
 								{{end}}