Ensure default gpg settings not nil and found commits have reference to repo (#8604)

* Ensure defaultGPGSettings not nil

* Ensure that coerced commits gain a reference to the repo

* Add warning if trying to get defaultgpgsetting on an unattached commit

models/gpg_key.go

 	defaultGPGSettings, err := c.GetRepositoryDefaultPublicGPGKey(false)
 	if err != nil {
 		log.Error("Error getting default public gpg key: %v", err)
+	} else if defaultGPGSettings == nil {
+		log.Warn("Unable to get defaultGPGSettings for unattached commit: %s", c.ID.String())
 	} else if defaultGPGSettings.Sign {
 		if commitVerification := verifyWithGPGSettings(defaultGPGSettings, sig, c.Signature.Payload, committer, keyID); commitVerification != nil {
 			if commitVerification.Reason == BadSignature {

modules/git/commit_info.go

 		treeCommit = commit
 	} else if rev, ok := revs[""]; ok {
 		treeCommit = convertCommit(rev)
+		treeCommit.repo = commit.repo
 	}
 	return commitsInfo, treeCommit, nil
 }