Fix extra columns from `label` table (#8633)

* Fix extra fields from database

* Add migration to drop unneeded columns

* Fix lint

* Make sure the columns exist

models/issue_label.go

 	Color           string `xorm:"VARCHAR(7)"`
 	NumIssues       int
 	NumClosedIssues int
-	NumOpenIssues   int  `xorm:"-"`
-	IsChecked       bool `xorm:"-"`
-	QueryString     string
-	IsSelected      bool
+	NumOpenIssues   int    `xorm:"-"`
+	IsChecked       bool   `xorm:"-"`
+	QueryString     string `xorm:"-"`
+	IsSelected      bool   `xorm:"-"`
 }
 
 // APIFormat converts a Label to the api.Label format

models/migrations/migrations.go

 	NewMigration("update migration repositories' service type", dropColumnHeadUserNameOnPullRequest),
 	// v103 -> v104
 	NewMigration("Add WhitelistDeployKeys to protected branch", addWhitelistDeployKeysToBranches),
+	// v104 -> v105
+	NewMigration("remove unnecessary columns from label", removeLabelUneededCols),
 }
 
 // Migrate database to current version

models/migrations/v104.go

+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"xorm.io/xorm"
+)
+
+func removeLabelUneededCols(x *xorm.Engine) error {
+
+	// Make sure the columns exist before dropping them
+	type Label struct {
+		QueryString string
+		IsSelected  bool
+	}
+	if err := x.Sync2(new(Label)); err != nil {
+		return err
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+	if err := dropTableColumns(sess, "label", "query_string"); err != nil {
+		return err
+	}
+	if err := dropTableColumns(sess, "label", "is_selected"); err != nil {
+		return err
+	}
+	return sess.Commit()
+}