Undefined array key "add_more" when paragraphs field has cardinality 1 while running phpunit tests

Problem/Motivation

When a paragraphs field is configured with a cardinality of 1, Drupal does not render an "Add more" button. As a result, the add_more key is absent from the widget element array. paragraphs_ee.module accesses this key unconditionally triggering a PHP warning during PHPUnit test runs:

Warning: Undefined array key "add_more" in paragraphs_ee/paragraphs_ee.module on line 85

PHPUnit treats unexpected output — including PHP warnings — as an error, causing the test to fail even though the underlying functionality may work correctly.

Steps to reproduce

• Install paragraphs and paragraphs_ee.
• Create a content type with a paragraphs field and set its cardinality to 1.
• Optionally pre-fill the field with a paragraph item (e.g. via default value).
• Write a PHPUnit ExistingSite test that renders the paragraph add/edit form for that paragraph type.
• Run the test and observe the failure mentioned above

Proposed resolution

• check for existence of add_more key before accessing it

User interface changes

• none

API changes

• none

Data model changes

• none