Add unique page name check for edit pages, bug fixes in Form Template Generate and DB Array IO classes

src/DB/Extended/ArrayIO.php

@@ -236,7 +236,7 @@ class ArrayIO extends \CoreLibs\DB\IO
 	 */
 	public function getPkId(): int|string|null
 	{
-		return $this->pk_id;
+		return $this->pk_id ?? null;
 	}
 
 	/**

src/Output/Form/Generate.php

@@ -1507,7 +1507,7 @@ class Generate
 			}
 			if (
 				!empty($this->reference_array[$key]['mandatory']) &&
-				!$this->reference_array[$key]['selected'][0]
+				empty($this->reference_array[$key]['selected'][0])
 			) {
 				$this->msg .= sprintf(
 					$this->l->__('Please select at least one Element from field <b>%s</b>!<br>'),

src/Output/Form/TableArrays/EditPages.php

@@ -53,6 +53,7 @@ class EditPages implements Interface\TableArraysInterface
 					'value' => $_POST['name'] ?? '',
 					'output_name' => 'Page name',
 					'mandatory' => 1,
+					'error_check' => 'unique',
 					'type' => 'text'
 				],
 				'order_number' => [