[Fix] 0047057 UI: Select field must not have more than one selected option

[fhelfer]

When the select value was 0 (e.g. DataTable action dropdown), both the
placeholder option and the option with value "0" got selected="selected"
because PHP treats 0 as falsy. Use explicit empty check (value === null
|| value === '') for placeholder selection and clear SELECTED for
non-matching options so only one option is ever selected.

Problem

• HTML-Validator: "The 'select' element cannot have more than one selected 'option' descendant unless the 'multiple' attribute is specified."
• Trat z. B. bei DataTable-Aktions-Dropdown mit Wert 0 ("some action") auf: Platzhalter "Bitte auswählen" und Option value="0" hatten beide selected.

Lösung

• Leerer Wert explizit prüfen: $value_is_empty = ($value === null || $value === '') statt !$value.
• Platzhalter nur bei echt leerem Wert als selected markieren.
• In der Options-Schleife SELECTED nur für die passende Option setzen, sonst leer.

Error: The “select” element cannot have more than one selected “option” descendant unless the “multiple” attribute is specified.
https://mantis.ilias.de/view.php?id=47057

[Annett7811]

Hello!

From an accessibility perspective, this looks good. Thank you very much for your work.

Best regards,

Annett

[oliversamoila]

Hello together,
Thank you very much for your contribution, @fhelfer. Thanks you for your review, @Annett7811. I agree and don't see these issues anymore.
I'm forwarding this to @thibsy for code review. He may contact you with change requests or incorporate the changes directly (That includes cherry picking too.)

Kind regards,
@oliversamoila (as UI coordinator)

[thibsy]

Hi @fhelfer,

Thx a lot for your contribution to the UI framework!

Please implement the following changes:

• Ternary: please replace this ternary operation with a dedicated if statement/block. We generally try to avoid ternary, because it decreases readability. While reading your code, I just had to double check that you do not set the selected-attribute all the time.
• $value_is_empty: please a) reuse the new variable and negate it, and b) remove the ternary operation here as well.

Sorry for the nitpicks.

Kind regards,
@thibsy (as UI coordinator)

[thibsy]

Hi @fhelfer,

Thx a lot for implementing the requested changes. This was a lot easier to review now =). Changes LGTM now.

Kind regards,
@thibsy (as UI coordinator)