di_Binding.Resolver ignores optional bindings when platform cache is off

[ImJohnMDaniel]

In the di_Binding.Resolver.get() method, if the di_PlatformCache.getInstance().retrieveBindings(String, Schema.SObjectType) method does not return matchedBindings and di_Binding.Resolver.bindingsAreRequired is false (which means "empty bindings are allowed"), then the logic from the loadBindings() method is never called.