Fixed: Return better error message if username or password is null

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

src/Lidarr.Http/Authentication/AuthenticationModule.cs

@@ -3,10 +3,6 @@ using Nancy;
 using Nancy.Authentication.Forms;
 using Nancy.Extensions;
 using Nancy.ModelBinding;
-using NzbDrone.Common.Extensions;
-using NLog;
-using NzbDrone.Common.Instrumentation;
-using NzbDrone.Core.Authentication;
 using NzbDrone.Core.Configuration;
 
 namespace Lidarr.Http.Authentication
@@ -30,7 +26,8 @@ namespace Lidarr.Http.Authentication
 
             if (user == null)
             {
-                return LoginFailed();
+                var returnUrl = (string)Request.Query.returnUrl;
+                return Context.GetRedirect($"~/login?returnUrl={returnUrl}&loginFailed=true");
             }
 
             DateTime? expiry = null;
@@ -49,11 +46,5 @@ namespace Lidarr.Http.Authentication
 
             return this.LogoutAndRedirect(_configFileProvider.UrlBase + "/");
         }
-
-        private Response LoginFailed()
-        {
-            var returnUrl = (string)Request.Query.returnUrl;
-            return Context.GetRedirect($"~/login?returnUrl={returnUrl}&loginFailed=true");
-        }
     }
 }

src/NzbDrone.Core/Authentication/UserService.cs

@@ -73,6 +73,11 @@ namespace NzbDrone.Core.Authentication
 
         public User FindUser(string username, string password)
         {
+            if (username.IsNullOrWhiteSpace() || password.IsNullOrWhiteSpace())
+            {
+                return null;
+            }
+
             var user = _repo.FindUser(username.ToLowerInvariant());
 
             if (user == null)