Added hidden element before multiselect form elements in adminhtml

[Hanmac]

Description (*)

This makes it possible for a Multiselect EAV Attribute to set no values inside a store view while the global settings still has values.

Related Pull Requests

Fixed Issues (if relevant)

1. Fixes Product EAV and MultiSelect problem with StoreView and Default #2065

Manual testing scenarios (*)

1. Create an Product EAV Attribute with Multiselect as Input and StoreView
2. Configure the Product in Global Store to have some values in the input
3. go so store specific config, now simultaneously disable the "Use Default Value" Option AND also remove all elements from the list
4. the empty value for StoreView can't be saved at the same time as "Use Default Value" is disabled (because the hidden input is missing)

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)
• Add yourself to contributors list

[fballiano]

I can't replicate the problem, here's my test, on the main branch

this is the default scope, with 3 selected values

and on the store_view scope I can save the product removing all 3 selected values, with no issue:

[Piralein]

2023-07-04.09-46-38.mp4

[fballiano]

mmm ok I got it, if you first unselect some values (but not all) and save, then unselect everything and save again, then it works.

but unselecting everything at the first round and saving doesn't work

[fballiano]

tested, works perfectly