modal_menu: Displaying the correct placeholder from the option

[infograf768]

Pull Request for Issue #16421

Summary of Changes

Adding conditionals to display the default placeholder with null value defined in the field Option

Testing Instructions

Edit an item which contains a choice for a menu item field using the modal_menu type.

1. Creating a Menu Item Alias. Choosing the menu item to alias to.
2. Creating a Create Article menu item. Choosing the menu item Submission Redirect in Options.
3. Creating a Login Form menu item. Choosing the Menu Item Login Redirect and Menu Item Logout Redirect in the Options.
4. Creating a Logout menu item. Choosing the Logout Redirection Page in the Options.
5. Editing the Site Login Form module. Choosing the Login Redirection Page and the Logout Redirection Page.
6. Editing the Site Menu module. Choosing the Base Item.

The xml code for the Menu module is for example

				<field
					name="base"
					type="modal_menu"
					label="MOD_MENU_FIELD_ACTIVE_LABEL"
					description="MOD_MENU_FIELD_ACTIVE_DESC"
					select="true"
					new="true"
					edit="true"
					clear="true"
					>
					<option value="">JCURRENT</option>
				</field>

In each case, select a menu item in the modal. Then Clear that menu item.

Expected result for the placeholder value

1. Select a Menu Item
2. Default
3. Default for both
4. Default
5. Default for both
6. Current

Actual result

All have Select a Menu Item

Patch and test again. Do not forget to choose a menu item and Clear to confirm that the correct value is displayed.

Here is an example —after patch— concerning the original issue with Menu module.

@epidote

[AlexRed]

I have tested this item ✅ successfully on 113c374

Patch ok for me

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[Bakual]

Looks a bit wrong to me to use the <option> tag for this. The tag could be present more than once but your code only supports one. So imho it would make more sense to use an attribute (eg placeholder or whatever you like) of the field instead a child element.

[infograf768]

this pr deals with existing xmls. its purpose was not to refactor them.
if you think we should, then let's do this, but it means modifying each of them.

btw, the option is NOT supposed to be used more than once per field.

[Bakual]

Ah sorry, yes then of course we need to take what is there already.

[carcam]

I have tested this item ✅ successfully on 113c374

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[ghost]

RTC after two successful tests.