Editing a macro that has a picker allowing multiple options merges the selected options instead of displaying them separately.

Steps to reproduce:

1. Insert inside a page a macro that has a picker allowing multiple options. i.e. PDF viewer macro.
2. Fill the parameter that allows multiple options with two or more entries.
3. Submit
4. Edit the macro

Expected results:

The previously filled parameter displays the entries separately, as they were when the macro was created.

Actual results:

The previously filled parameter displays the entries merged into one.

The issue is also described here: https://github.com/xwikisas/macro-pdfviewer/issues/43