Fix nil checking on typed interface (#17598)

* Fix nil checking on typed interface

- Partially resoles #17596
- Resolves SA4023 errors.
- Ensure correctly that typed interface are nil.

* Remove unnecessary code

`NewBleveIndexer` will never return nil, even on errors.

* Patch `NewBleveIndexer`

* Fix low-level functions

* Remove deadcode

* Fix GetSession

* Close Elastic search when err isn't nil

* Update elastic_search.go

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/base.go

@@ -130,14 +130,6 @@ func Recovery() func(next http.Handler) http.Handler {
 					log.Error("%v", combinedErr)
 
 					sessionStore := session.GetSession(req)
-					if sessionStore == nil {
-						if setting.IsProd {
-							http.Error(w, http.StatusText(500), 500)
-						} else {
-							http.Error(w, combinedErr, 500)
-						}
-						return
-					}
 
 					var lc = middleware.Locale(w, req)
 					var store = dataStore{