Merge branch 'CheckFileExistsBeforeZip' of https://github.com/mannes/h5p-php-library into mannes-CheckFileExistsBeforeZip

h5p.classes.php

@@ -1610,8 +1610,10 @@ Class H5PExport {
     foreach ($files as $file) {
       // Please note that the zip format has no concept of folders, we must
       // use forward slashes to separate our directories.
+      if (file_exists(realpath($file->absolutePath))) {
         $zip->addFile(realpath($file->absolutePath), $file->relativePath);
       }
+    }
 
     // Close zip and remove tmp dir
     $zip->close();