Datepicker not rendering nexticon and previousicon if custom templates are used

[andrebernardini]

Describe the bug

If custom templates are used in the datepicker for previousicon and nexticon, the buttons are rendered without any content.

Pull Request Link

No response

Reason for not contributing a PR

• Lack of time
• Unsure how to implement the fix/feature
• Difficulty understanding the codebase
• Other

Other Reason

No response

Reproducer

https://stackblitz.com/edit/fjruux2y?file=src%2Fapp%2Fdatepicker-basic-demo.html

Environment

N/A (stackblitz provided)

Angular version

19.1.6

PrimeNG version

v19

Node version

No response

Browser(s)

No response

Steps to reproduce the behavior

With the provided Stackblitz example:

1. Visit the URL and wait until everything is compiled and started
2. Open the datepicker
3. Inspect the state of the previousbutton (the one to navigate to the previous month).

Previousbutton uses a custom template for its icon while the nextbutton does not (if you use a custom template for nexticon, the same problem will appear there).

Expected behavior

Custom template should be rendered inside the button