Project wizard template text field with button not udated when filled as text

When using the Gemoc project wizard, in the template part, we use AbstractStringWithButtonOption
to set the ecore file or k3 project.

It works correctly if we use the button, but if we set the text directly in the text field, then the data is not taken into account.
(see https://github.com/eclipse/gemoc-studio-modeldebugging/tree/master/javaAbstractStringWithButtonOption_execution/java_xdsml/plugins/org.eclipse.gemoc.execution.sequential.javaxdsml.ide.ui/src/org/eclipse/gemoc/execution/sequential/javaxdsml/ide/ui/templates)

step to reproduce:
* get some ecore project (for example, import an official sample)
* File > new > create GEMOC Sequential xDSML project
* next, select one of the templates,
* directly set your ecore file in the text field (not using the browse button)

It will generate a project without the ecore file set (as if the user hasn't put any information)