Adds null check for files

Author: jaapio

src/phpDocumentor/Reflection/Php/ProjectFactory.php

@@ -76,7 +76,10 @@ public function create($name, array $files)
 
         foreach ($files as $filePath) {
             $strategy = $this->strategies->findMatching($filePath);
-            $project->addFile($strategy->create($filePath, $this->strategies));
+            $file = $strategy->create($filePath, $this->strategies);
+            if ($file !== null) {
+                $project->addFile($file);
+            }
         }
 
         $this->buildNamespaces($project);