提交代码，解决Bug

Signed-off-by: zouap <zouap@pcl.ac.cn>

models/issue.go

@@ -842,13 +842,20 @@ func (issue *Issue) GetLastEventLabel() string {
 // GetLastComment return last comment for the current issue.
 func (issue *Issue) GetCloseUser() (*User, error) {
 	var c Comment
-	exist, err := x.Where("type = ?", CommentTypeClose).
+	tmp := CommentTypeClose
+	if issue.IsPull {
+		tmp = CommentTypeMergePull
+	}
+	exist, err := x.Where("type = ?", tmp).
 		And("issue_id = ?", issue.ID).Desc("id").Get(&c)
 	if err != nil {
 		return nil, err
 	}
 	if !exist {
-		return nil, nil
+		if issue.Poster == nil {
+			issue.LoadPoster()
+		}
+		return issue.Poster, nil
 	}
 	err = c.LoadPoster()
 	if c.Poster != nil {