Fixed: Prevent unknown settings implementation from failing to deserialize

(cherry picked from commit 0e2cc7851f556e928e52bb2886c7d60c13b0741e)

Log removal of invalid definitions as warnings

(cherry picked from commit 3d61719a2cc9c87ac3c92b5358bb5034aed4c2ff)

src/NzbDrone.Core/ThingiProvider/ProviderFactory.cs

@@ -169,14 +169,13 @@ namespace NzbDrone.Core.ThingiProvider
             definition.Message = provider.Message;
         }
 
-        // TODO: Remove providers even if the ConfigContract can't be deserialized (this will fail to remove providers if the settings can't be deserialized).
         private void RemoveMissingImplementations()
         {
             var storedProvider = _providerRepository.All();
 
             foreach (var invalidDefinition in storedProvider.Where(def => GetImplementation(def) == null))
             {
-                _logger.Debug("Removing {0} ", invalidDefinition.Name);
+                _logger.Warn("Removing {0}", invalidDefinition.Name);
                 _providerRepository.Delete(invalidDefinition);
             }
         }

src/NzbDrone.Core/ThingiProvider/ProviderRepository.cs

@@ -54,7 +54,7 @@ namespace NzbDrone.Core.ThingiProvider
                     var item = parser(reader);
                     var impType = typeof(IProviderConfig).Assembly.FindTypeByName(item.ConfigContract);
 
-                    if (body.IsNullOrWhiteSpace())
+                    if (body.IsNullOrWhiteSpace() || impType == null)
                     {
                         item.Settings = NullConfig.Instance;
                     }