Error when clicking 'New Doc' in Files view

In DOCman 1.5.6/1.5.7, there's a bug that causes an error when clicking 'New Doc' in the backend files view. The resulting error looks something like this:

string(2) "23" array(1) { [0]=> string(12) "filename.ext" } 

This issue will be fixed in DOCman 1.5.8. In the meantime, you can solve the problem like this:

• Open the file administrator/components/com_docman/includes/files.php
• Find the following code:

  var_dump(__METHOD__.__LINE__, $cid );die;

  (around line 23)
• Replace it with the following code:

  if(!$cid[0]) {
      JFactory::getApplication()
      ->redirect("index.php?option=com_docman§ion=files", 
      _DML_MAKE_SELECTION);
  }