Disable action param not honored

in the demo app, use

prog model >Composite Value Types

The page object shows a single value (a complex number type) which starts off being set to 1+0i.  The idea of the "addComplexNumber" action is to allow the end-user to add a value to this, eg "2 +3i" to result in "3 + 3i".  To make it more obvious that they are adding to the value held by the page object, the first parameter of this action is defaulted to the value from the page object, and is set to be disabled.

The defaulting works fine, and the UI looks fine:

, however... it IS actually possible to click into the disabled field and set a value: