Fix deadline on update issue or PR via API (#8699)

routers/api/v1/repo/issue.go

 	}
 
 	// Update the deadline
-	var deadlineUnix util.TimeStamp
 	if form.Deadline != nil && !form.Deadline.IsZero() && ctx.Repo.CanWrite(models.UnitTypeIssues) {
-		deadlineUnix = util.TimeStamp(form.Deadline.Unix())
-	}
-
-	if err := models.UpdateIssueDeadline(issue, deadlineUnix, ctx.User); err != nil {
-		ctx.Error(500, "UpdateIssueDeadline", err)
-		return
+		deadlineUnix := util.TimeStamp(form.Deadline.Unix())
+		if err := models.UpdateIssueDeadline(issue, deadlineUnix, ctx.User); err != nil {
+			ctx.Error(500, "UpdateIssueDeadline", err)
+			return
+		}
+		issue.DeadlineUnix = deadlineUnix
 	}
 
 	// Add/delete assignees

routers/api/v1/repo/pull.go

 	}
 
 	// Update Deadline
-	var deadlineUnix util.TimeStamp
 	if form.Deadline != nil && !form.Deadline.IsZero() {
-		deadlineUnix = util.TimeStamp(form.Deadline.Unix())
-	}
-
-	if err := models.UpdateIssueDeadline(issue, deadlineUnix, ctx.User); err != nil {
-		ctx.Error(500, "UpdateIssueDeadline", err)
-		return
+		deadlineUnix := util.TimeStamp(form.Deadline.Unix())
+		if err := models.UpdateIssueDeadline(issue, deadlineUnix, ctx.User); err != nil {
+			ctx.Error(500, "UpdateIssueDeadline", err)
+			return
+		}
+		issue.DeadlineUnix = deadlineUnix
 	}
 
 	// Add/delete assignees