Fix on Page->getText() and Page->getTextArray()

In some PDFs, the content of the page is an instance of ElementNull, in those cases getText() and getTextArray() fails on getting the text: Call to undefined method Smalot\PdfParser\Element\ElementNull::getText()

src/Smalot/PdfParser/Page.php

@@ -33,6 +33,7 @@
 use Smalot\PdfParser\Element\ElementArray;
 use Smalot\PdfParser\Element\ElementMissing;
 use Smalot\PdfParser\Element\ElementXRef;
+use Smalot\PdfParser\Element\ElementNull;
 
 /**
  * Class Page
@@ -185,6 +186,8 @@ public function getText(Page $page = null)
 
             if ($contents instanceof ElementMissing) {
                 return '';
+			} elseif ($contents instanceof ElementNull) {
+				return '';
             } elseif ($contents instanceof Object) {
                 $elements = $contents->getHeader()->getElements();
 
@@ -231,6 +234,8 @@ public function getTextArray(Page $page = null)
 
 			if ($contents instanceof ElementMissing) {
 				return array();
+			} elseif ($contents instanceof ElementNull) {
+				return array();
 			} elseif ($contents instanceof Object) {
 				$elements = $contents->getHeader()->getElements();