8031359: Invocable.getInterface() works incorrectly if interface has default methods
Reviewed-by: attila, hannesw
x undefined? trueTypeError: Cannot read property "foo" from undefinedTypeError: Cannot set property "bar" of undefinedTypeError: Cannot read property "1" from undefinedTypeError: Cannot set property "0" of undefinedTypeError: Cannot read property "func" from undefinedTypeError: Cannot delete property "0" of undefinedTypeError: Cannot delete property "foo" of undefinedTypeError: undefined is not an ObjectTypeError: Cannot apply "with" to undefined