Module Properties viewer doesn't show *open* modules

To reproduce:
* From a java project,
* Go to *Build Path* Configuration
* Set *modular* on the Module Path entry and click "Edit" to open the Module Properties viewer
* In *Details* tab, click *Add...* beside the *Added exports* viewer
* Add an internal JDK package (eg `jdk.compiler`) and one of its package (eg `com.sun.source.tree`); and set it as *opens* (instead of *exports*).
* Click OK.

Expected: something visible
Got: blank line in the viewer

Here is a video showcasing this reproducer.
[Screencast from 2023-11-14 09-29-07.webm](https://github.com/eclipse-jdt/eclipse.jdt.ui/assets/469058/ca364b36-0f23-4113-a3db-71e0d06271c6)
This is also happening with 4.29 (ie not a regression in 4.30)

Reproduce the problem in a Java project through Build Path Configuration, the Module Path entry, and the Module Properties viewer's Details tab. Inspect the viewer handling for an added package marked as opens; done means the open module and package are visibly represented instead of appearing as a blank line.

Written by the indexing model from the issue text.