fix(container.class): Prevent item creation with null value for mandatory fields

[TarekRemo]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !45283
• Before this fix, in preItem(), the validation of required fields (validateValues()) was only called if populateData() did not return false. However, populateData() returns false when none of the block's fields are present in the input. Result: A creation that did not submit the fields (API/CLI, or a form without mapping) completely bypassed the check and created the element with a NULL value in a required field.
• Fix: On creation only (isNewItem()), when populateData() returns false and the continer type is dom, validateValues() is still called on an empty dataset, which causes the missing required fields to fail validation and blocks creation.

[Rom1-B]

The minimal $data array built for this new validation path omits the status field. populateData()'s normal path always sets $data[$status_field_name] from $item->input/$item->fields (lines 2029-2034), and validateValues() resolves $status_value = $data[$status_field_name] ?? null to apply PluginFieldsStatusOverride mandatory/readonly relaxations (line 1673). Since this new branch never sets that key, any status override waiving a field's mandatory flag for a given creation status is silently ignored here, so a legitimate creation (API/CLI, dom container, status override in place) gets incorrectly blocked.

Suggested change

	if ($item->isNewItem() && $loc_c->fields['type'] === 'dom') {
	$data = ['plugin_fields_containers_id' => $c_id];
	if (self::validateValues($data, $item::getType(), isset($_REQUEST['massiveaction'])) === false) {
	$item->input = [];
	return false;
	}
	}
	if ($item->isNewItem() && $loc_c->fields['type'] === 'dom') {
	$status_field_name = PluginFieldsStatusOverride::getStatusFieldName($item::getType());
	$data = ['plugin_fields_containers_id' => $c_id];
	if (array_key_exists($status_field_name, $item->input) && $item->input[$status_field_name] !== '') {
	$data[$status_field_name] = (int) $item->input[$status_field_name];
	} elseif (array_key_exists($status_field_name, $item->fields) && $item->fields[$status_field_name] !== '') {
	$data[$status_field_name] = (int) $item->fields[$status_field_name];
	}
	if (self::validateValues($data, $item::getType(), isset($_REQUEST['massiveaction'])) === false) {
	$item->input = [];
	return false;
	}
	}

[TarekRemo]

done