Changed init value of the NumberingLevel.alignment property.

Author: Roman Syroeshko

src/PhpWord/Style/NumberingLevel.php

@@ -85,7 +85,7 @@ class NumberingLevel extends AbstractStyle
     /**
      * @var string
      */
-    private $alignment;
+    private $alignment = '';
 
     /**
      * Left

src/PhpWord/Writer/Word2007/Part/Numbering.php

@@ -114,11 +114,12 @@ private function writeLevel(XMLWriter $xmlWriter, NumberingLevel $level)
             'pStyle'    => 'pStyle',
             'suffix'    => 'suff',
             'text'      => 'lvlText',
-            'alignment' => 'lvlJc'
+            'alignment' => 'lvlJc',
         );
         foreach ($properties as $property => $nodeName) {
             $getMethod = "get{$property}";
-            if (!is_null($level->$getMethod())) {
+            if ('' !== $level->$getMethod()         // this condition is now supported by `alignment` only
+                && !is_null($level->$getMethod())) {
                 $xmlWriter->startElement("w:{$nodeName}");
                 $xmlWriter->writeAttribute('w:val', $level->$getMethod());
                 $xmlWriter->endElement(); // w:start