Fix rare PclZip/realpath/PHP version problem

In PHP 5.4.4 realpath() handles absolute paths correctly, but in PHP 5.3.8 returns false.

Author: andrew-kzoo

src/PhpWord/Shared/ZipArchive.php

@@ -218,7 +218,10 @@ public function pclzipAddFile($filename, $localname = null)
     {
         /** @var \PclZip $zip Type hint */
         $zip = $this->zip;
-        $filename = realpath($filename);
+        $test_filename = realpath($filename);
+        if($test_filename !== false) {
+            $filename = $test_filename;
+        }
         $filenameParts = pathinfo($filename);
         $localnameParts = pathinfo($localname);