Should fix "undefined property" ->attributes.

Author: rasamassen

tests/PhpWordTests/Writer/HTML/Element/TableTest.php

@@ -199,7 +199,7 @@ public function testWriteTableCellVAlign(): void
         $cell3Query = $xpath->query('//table/tr/td[3]');
         self::assertNotFalse($cell3Query);
         self::assertCount(1, $cell3Query);
-
+        self::assertObjectHasProperty('attributes', $cell3Query->item(0));
         $cell3Style = $cell3Query->item(0)->attributes->getNamedItem('style');
         self::assertNull($cell3Style);
     }
@@ -232,6 +232,7 @@ public function testWriteTableCellVMerge(): void
         $cell3Query = $xpath->query('//table/tr[3]/td[1]');
         self::assertNotFalse($cell3Query);
         self::assertCount(1, $cell3Query);
+        self::assertObjectHasProperty('attributes', $cell3Query->item(0));
         self::assertNull($cell3Query->item(0)->attributes->getNamedItem('rowspan'));
     }
 }