FIX: simplexml_load_string() can return FALSE PHPOffice#2

Author: Frederic Delaunay

src/PhpSpreadsheet/Reader/Xlsx.php

@@ -1637,11 +1637,11 @@ public function load($pFilename)
                                                 }
                                             }
                                         }
-                                        if (FALSE !== $xmlDrawingElem = simplexml_load_string(
+                                        if (FALSE !== ($xmlDrawingElem = simplexml_load_string(
                                             $this->securityScan($this->getFromZipArchive($zip, $fileDrawing)),
                                             'SimpleXMLElement',
                                             Settings::getLibXmlLoaderOptions()
-                                        ))
+                                        )))
                                         {
                                           $xmlDrawing = $xmlDrawingElem->children('http://schemas.openxmlformats.org/drawingml/2006/spreadsheetDrawing');
 
@@ -1779,16 +1779,18 @@ public function load($pFilename)
                                     }
 
                                     // unparsed drawing AlternateContent
-                                    $xmlAltDrawing = simplexml_load_string(
+                                    if (FALSE !== ($xmlAltDrawingElem = simplexml_load_string(
                                         $this->securityScan($this->getFromZipArchive($zip, $fileDrawing)),
                                         'SimpleXMLElement',
                                         Settings::getLibXmlLoaderOptions()
-                                    )->children('http://schemas.openxmlformats.org/markup-compatibility/2006');
-
-                                    if ($xmlAltDrawing->AlternateContent) {
-                                        foreach ($xmlAltDrawing->AlternateContent as $alternateContent) {
-                                            $unparsedLoadedData['sheets'][$docSheet->getCodeName()]['drawingAlternateContents'][] = $alternateContent->asXML();
-                                        }
+                                    )))
+                                    {
+                                      $xmlAltDrawing = $xmlAltDrawingElem->children('http://schemas.openxmlformats.org/markup-compatibility/2006');
+                                      if ($xmlAltDrawing->AlternateContent) {
+                                          foreach ($xmlAltDrawing->AlternateContent as $alternateContent) {
+                                              $unparsedLoadedData['sheets'][$docSheet->getCodeName()]['drawingAlternateContents'][] = $alternateContent->asXML();
+                                          }
+                                      }
                                     }
                                 }
                             }