Radios Other element triggers PHP deprecation warning when used with conditional visibility

Problem/Motivation

When using the Radios Other element type in a Webform and configuring conditional visibility on another field based on the value of the Radios Other element, the following PHP deprecation warning is triggered:

Using null as an array offset is deprecated, use an empty string instead in
/webform/src/Plugin/WebformElement/OptionsBase.php

The warning originates from the following line in OptionsBase.php:

return (isset($options[$value])) ? $value : NULL;

Steps to reproduce

• Create a Webform.
• Add a Radios Other element with multiple options.
• Add another field, such as a text field.
• Configure conditional visibility on the second field based on the selected value of the Radios Other element.
• Open the Webform and trigger the conditional visibility evaluation.

Proposed resolution

Add a check to ensure that $value is not NULL before using it as an array offset.

For example:

return (isset($value) && isset($options[$value])) ? $value : NULL;

This would prevent the deprecation warning when $value is NULL while preserving the existing behavior for valid option values.

Remaining tasks

User interface changes

API changes

Data model changes