Fixed: Ignore empty tags when adding items to Flood

(cherry picked from commit 0a5200766ea80fc1c97bfa497cdfed31b9af687f)

src/NzbDrone.Core/Download/Clients/Flood/Flood.cs

@@ -70,7 +70,7 @@ namespace NzbDrone.Core.Download.Clients.Flood
                 }
             }
 
-            return result;
+            return result.Where(t => t.IsNotNullOrWhiteSpace());
         }
 
         public override string Name => "Flood";