-error:
When adding a binding to an InputActionMap, there is a check to make sure the binding's path is not null:
In order to add a placeholder binding that will be bound later, the path can be set to an empty string instead.

However, if the asset (or even just the map) is cloned through json, any empty strings in the bindings are converted to null when they are loaded.
This results in a map that has a binding with a null path, which isn't supposed to be allowed.

-repro:
--open attached project
--open Test Runner window
--run the test
--NOTICE it fails