Autofrac Parameter name: serviceType null exception

Hello,

My plugin-controller is throwing this unusual error when I attempt to install my new plugin.

I am using a copy of the source from: 'Payments.PayPalDirect' and I've updated my build-path, names of files etc. - so it appears normally in the available plugins list as "Uninstalled"   

This happens when I go to install the plugin:

System.ArgumentNullException: Value cannot be null. Parameter name: serviceType at Autofac.Util.Enforce.ArgumentNotNull[T](T value, String name) at Autofac.Core.TypedService..ctor(Type serviceType) at Autofac.ResolutionExtensions.TryResolve(IComponentContext context, Type serviceType, Object& instance) at Nop.Core.Plugins.PluginDescriptor.Instance[T]() in C:\bin\nopCommerce_2.20_Source\Libraries\Nop.Core\Plugins\PluginDescriptor.cs:line 89 at Nop.Core.Plugins.PluginDescriptor.Instance() in C:\bin\nopCommerce_2.20_Source\Libraries\Nop.Core\Plugins\PluginDescriptor.cs:line 109 at Nop.Admin.Controllers.PluginController.Install(String systemName) in C:\bin\nopCommerce_2.20_Source\Presentation\Nop.Web\Administration\Controllers\PluginController.cs:line 82 

Hello,

My plugin-controller is throwing this unusual error when I attempt to install my new plugin.

I am using a copy of the source from: 'Payments.PayPalDirect' and I've updated my build-path, names of files etc. - so it appears normally in the available plugins list as "Uninstalled"   

This happens when I go to install the plugin:

System.ArgumentNullException: Value cannot be null. Parameter name: serviceType at Autofac.Util.Enforce.ArgumentNotNull[T](T value, String name) at Autofac.Core.TypedService..ctor(Type serviceType) at Autofac.ResolutionExtensions.TryResolve(IComponentContext context, Type serviceType, Object& instance) at Nop.Core.Plugins.PluginDescriptor.Instance[T]() in C:\bin\nopCommerce_2.20_Source\Libraries\Nop.Core\Plugins\PluginDescriptor.cs:line 89 at Nop.Core.Plugins.PluginDescriptor.Instance() in C:\bin\nopCommerce_2.20_Source\Libraries\Nop.Core\Plugins\PluginDescriptor.cs:line 109 at Nop.Admin.Controllers.PluginController.Install(String systemName) in C:\bin\nopCommerce_2.20_Source\Presentation\Nop.Web\Administration\Controllers\PluginController.cs:line 82 

Does your plugin have a "DependencyRegistrar" class and if so can you provide the code from it?