NullPage::parent() now returns a NullPage instead of null — undocumented BC break (a7884201)

[adrianbj]

Short description of the issue

Commit a7884201 ("Improvements to NullPage class") changed NullPage::parent() to return a freshly-allocated NullPage rather than null. The phpdoc still says @return null. Callers doing strict-null checks (if($page->parent() === null)) silently change behavior.

Expected behavior

Either keep returning null (semantically a non-existent page has no parent), or update the phpdoc and call this out in the changelog as a BC break.

Actual behavior

wire/core/NullPage.php:84-89:

public function parent($selector = '') {
    return $this->wire()->pages->newNullPage(true);
}

The forceNew=true argument also means every call allocates a fresh NullPage, so $page->parent()->parent() builds N new objects.

Optional: Suggestion for a possible fix

Either:

1. Restore return null; and update phpdoc.
2. If the new behavior is intentional, cache the NullPage and update phpdoc to @return NullPage. Add a note to the upgrade docs.

Setup/Environment

• ProcessWire version: dev @ 15c749ed
• File: wire/core/NullPage.php:84-89
• Changed in commit a7884201