From the reference guide's page Moving from 4 to 5
The parameterless constructor for UserAction has been removed. Constructing a UserAction always requires an IContext now. Changes are only necessary for custom user actions which are NOT defined as custom Java action in the Modeler, e.g. an action which replaces the LoginAction using an action listener.
From the log it states that you're calling a method and missing a method argument, the context. Likely a function has changed in the new Mx version and this change is not reflected in your code yet.