BUGFIX: Access isNil function from Helper function to apply selected image to property

[crydotsnake]

Upgrade instructions

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Review instructions

Follow-up to: #5117

With the latest Bugfix release of Neos 8.3.14 currently when selecting an image from the media browser it not will be applyied to the image property as the IsNil function has to be accessed inside of the Helper function.

NeosCMS.isNil()

In this case, leads to an unresolved function or method.

Before

https://github.com/neos/neos-development-collection/assets/39345336/ed761221-924d-467f-bd9f-6eb6c97dd553

After

https://github.com/neos/neos-development-collection/assets/39345336/2c78211a-c8a8-4f55-808a-15b495fde586

Checklist

• [x] Code follows the PSR-2 coding style
• [ ] Tests have been created, run and adjusted as needed
• [x] The PR is created against the lowest maintained branch
• [ ] Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• [ ] Reviewer - The first section explains the change briefly for change-logs
• [ ] Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[kitsunet]

Lovely with the video, thanks a lot <3