Calendar not working with empty date field included in a structure field

[animaux]

Description

When having an empty date field inside a structure field and trying to use the calendar date picker, only a small black square is showing up.  After entering a value by hand the calendar works as expected.

Expected behavior

The calendar date picker should open.

Screenshots

To reproduce

Create a page with the following field in the blueprint:

termine:
  label: Termine
  type: structure
  fields:
    datum:
      label: Datum
      type: date
      width: 1/3
      required: true

Your setup

Kirby Version
4.2.0 (PHP 8.3.6)

Console output

RangeError: Array length must be a positive integer of safe magnitude.

Your system (please complete the following information)

• Device: mac Mini 2018 (Intel)
• OS: macOS 14.4.1
• Browser: Safari
• Version: 17.4.1