Image option in page blueprint fails when set to plain query string

[rasteiner]

Description

Setting the image option of a page blueprint to a query string throws a 500 error in the panel when trying to show the page in a pages section.

Expected behavior
It should be possible to set the image option of a page blueprint to a string, as documented here:
https://getkirby.com/docs/reference/panel/blueprints/page#image-options

To reproduce

1. Install plainkit
2. Edit site/blueprints/pages/default.yml to include an image option:

   image: page.image

3. Install and enter into panel
4. See error

Your setup

Kirby Version: 4.4.1 (don't think it's a "recent" regression though).

Console output

{
    "status": "error",
    "message": "array_merge(): Argument #3 must be of type array, string given",
    "code": 500,
    "exception": "TypeError",
    "key": null,
    "file": "\/kirby\/src\/Panel\/Model.php",
    "line": 134,
    "details": [],
    "route": "pages\/([a-zA-Z0-9\\.\\-_%= \\+\\@\\(\\)]+)\/sections\/([a-zA-Z0-9\\.\\-_%= \\+\\@\\(\\)]+)"
}

Fix

I think the $blueprint variable here:

kirby/src/Panel/Model.php

Lines 108 to 125 in eb47158

	$blueprint = $this->model->blueprint()->image();
	if ($blueprint === false) {
	if (empty($settings) === true) {
	return null;
	}
	$blueprint = null;
	}
	// skip image thumbnail if option
	// is explicitly set to show the icon
	if ($settings === 'icon') {
	$settings = ['query' => false];
	} elseif (is_string($settings) === true) {
	// convert string settings to proper array
	$settings = ['query' => $settings];
	}

Needs the same treatment as the $settings variable: transform it into an array when it's a string different from "icon".

Workaround

Pass an array to the image option:

image:
  query: page.image