Disposing a container with no extensions causes a NullReferenceException

[FodderMK]

The following code causes a NullReferenceException:

var injector = new InjectionContainer();
injector.Dispose();

This is caused by the foreach loop in InjectionContainer.cs line 146 trying to loop through a list that hasn't been initialized. This can be fixed either checking for a null list before looping or changing line 26 to read:

private List<IContainerExtension> extensions = new List<IContainerExtension>();

[intentor]

Thanks for the feedback, @FodderMK! It'll be on the next release!