Steps to reproduce the issue

Tested Field-type Gallery on Article got on different Paths using Front- or Backend:

• Warning: JFolder: :files: Path is not a folder. Path: __/images/images/sampledata/fruitshop
• and Picture-Gallery: Warning: Invalid argument supplied for foreach() in /plugins/fields/gallery/tmpl/gallery.php on line 50
  

System information (as much as possible)

Joomla! 3.7.0-beta1-nightly
macOS Sierra, 10.12.2
Firefox 50.1.0
PHP 7.0.4
MySQLi 5.5.53-0