fix middleware user field

Author: streamtw

src/middleware/MultiUser.php

@@ -10,9 +10,9 @@ public function handle($request, Closure $next)
     {
     	if (\Config::get('lfm.allow_multi_user') === true) {
 	        if ($request->input('base') == null) {
-	            $request->merge(['base' => \Auth::user()->name]);
-	        } elseif (strpos($request->input('base'), \Auth::user()->name) === false) {
-	            $request->replace(['base' => \Auth::user()->name]);
+	            $request->merge(['base' => config('lfm.user_field')]);
+	        } elseif (strpos($request->input('base'), config('lfm.user_field')) === false) {
+	            $request->replace(['base' => config('lfm.user_field')]);
 	        }
 	    }