Merge pull request #280 from owncloud/bugfix/create-empty-file-with-e…

…mpty-string-no-null

In case $content is null file_put_contents fails badly

service/notesservice.php

@@ -148,7 +148,7 @@ public function update ($id, $content, $userId){
             $file->move($newFilePath);
         }
 
-        $file->putContent($content);
+        $file->putContent($content === null ? '' : $content);
 
         return Note::fromFile($file, $this->getTags($id));
     }