Fixes TypeFinder to not scan for types when the assembly IsDynamic (created using reflection Emit).

This fixes the RenderRouteHandlerTests which were failing due to a sequence of events when the new PetaPoco classes
were created using Reflection and then the TypeFinder tries to enumerate on them.

src/Umbraco.Core/TypeFinder.cs

@@ -407,6 +407,10 @@ namespace Umbraco.Core
 
 		private static IEnumerable<Type> GetTypesWithFormattedException(Assembly a)
 		{
+			//if the assembly is dynamic, do not try to scan it
+			if (a.IsDynamic)
+				return Enumerable.Empty<Type>();
+
 			try
 			{
 				return a.GetExportedTypes();