Fix git commit committer parsing and add some tests (#35007)

* Fix #34991
* Fix #34882

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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/commit_page.tmpl

@@ -147,7 +147,7 @@
 			<div class="flex-text-inline">
 				{{if or (ne .Commit.Committer.Name .Commit.Author.Name) (ne .Commit.Committer.Email .Commit.Author.Email)}}
 					<span class="text grey">{{ctx.Locale.Tr "repo.diff.committed_by"}}</span>
-					{{if ne .Verification.CommittingUser.ID 0}}
+					{{if and .Verification.CommittingUser .Verification.CommittingUser.ID}}
 						{{ctx.AvatarUtils.Avatar .Verification.CommittingUser 20}}
 						<a href="{{.Verification.CommittingUser.HomeLink}}"><strong>{{.Commit.Committer.Name}}</strong></a>
 					{{else}}