diff --git a/models/action.go b/models/action.go
index cd722cbe7..161a7220c 100644
--- a/models/action.go
+++ b/models/action.go
@@ -215,7 +215,7 @@ func (a *Action) getCommentLink(e Engine) string {
 		return "#"
 	}
 	if a.Comment == nil && a.CommentID != 0 {
-		a.Comment, _ = GetCommentByID(a.CommentID)
+		a.Comment, _ = getCommentByID(e, a.CommentID)
 	}
 	if a.Comment != nil {
 		return a.Comment.HTMLURL()
diff --git a/models/attachment.go b/models/attachment.go
index 81f2e15da..7e59c7eef 100644
--- a/models/attachment.go
+++ b/models/attachment.go
@@ -199,7 +199,7 @@ func GetAttachmentsByCommentID(commentID int64) ([]*Attachment, error) {
 
 func getAttachmentsByCommentID(e Engine, commentID int64) ([]*Attachment, error) {
 	attachments := make([]*Attachment, 0, 10)
-	return attachments, x.Where("comment_id=?", commentID).Find(&attachments)
+	return attachments, e.Where("comment_id=?", commentID).Find(&attachments)
 }
 
 // getAttachmentByReleaseIDFileName return a file based on the the following infos:
diff --git a/models/issue_comment.go b/models/issue_comment.go
index 3ba679021..2494467bf 100644
--- a/models/issue_comment.go
+++ b/models/issue_comment.go
@@ -749,8 +749,12 @@ func CreateRefComment(doer *User, repo *Repository, issue *Issue, content, commi
 
 // GetCommentByID returns the comment by given ID.
 func GetCommentByID(id int64) (*Comment, error) {
+	return getCommentByID(x, id)
+}
+
+func getCommentByID(e Engine, id int64) (*Comment, error) {
 	c := new(Comment)
-	has, err := x.ID(id).Get(c)
+	has, err := e.ID(id).Get(c)
 	if err != nil {
 		return nil, err
 	} else if !has {
diff --git a/modules/markup/common/linkify.go b/modules/markup/common/linkify.go
index 6ae70fba3..25621bf80 100644
--- a/modules/markup/common/linkify.go
+++ b/modules/markup/common/linkify.go
@@ -108,7 +108,7 @@ func (s *linkifyParser) Parse(parent ast.Node, block text.Reader, pc parser.Cont
 		}
 		at := bytes.IndexByte(line, '@')
 		m = []int{0, stop, at, stop - 1}
-		if m == nil || bytes.IndexByte(line[m[2]:m[3]], '.') < 0 {
+		if bytes.IndexByte(line[m[2]:m[3]], '.') < 0 {
 			return nil
 		}
 		lastChar := line[m[1]-1]
diff --git a/routers/repo/attachment.go b/routers/repo/attachment.go
index 96dc28a23..f938c230e 100644
--- a/routers/repo/attachment.go
+++ b/routers/repo/attachment.go
@@ -70,14 +70,14 @@ func UploadAttachment(ctx *context.Context) {
 func DeleteAttachment(ctx *context.Context) {
 	file := ctx.Query("file")
 	attach, err := models.GetAttachmentByUUID(file)
-	if !ctx.IsSigned || (ctx.User.ID != attach.UploaderID) {
-		ctx.Error(403)
-		return
-	}
 	if err != nil {
 		ctx.Error(400, err.Error())
 		return
 	}
+	if !ctx.IsSigned || (ctx.User.ID != attach.UploaderID) {
+		ctx.Error(403)
+		return
+	}
 	err = models.DeleteAttachment(attach, true)
 	if err != nil {
 		ctx.Error(500, fmt.Sprintf("DeleteAttachment: %v", err))
diff --git a/routers/repo/commit.go b/routers/repo/commit.go
index e581d3952..6a4b405e0 100644
--- a/routers/repo/commit.go
+++ b/routers/repo/commit.go
@@ -237,11 +237,11 @@ func Diff(ctx *context.Context) {
 	parents := make([]string, commit.ParentCount())
 	for i := 0; i < commit.ParentCount(); i++ {
 		sha, err := commit.ParentID(i)
-		parents[i] = sha.String()
 		if err != nil {
 			ctx.NotFound("repo.Diff", err)
 			return
 		}
+		parents[i] = sha.String()
 	}
 
 	ctx.Data["CommitID"] = commitID