It gives me `TypeError: 'bool' object is not iterable`.

See, `GaiaDataLayer.getAllMusic()` returns boolean, while execution of other scripts returns [].
`(Pdb) self.marionette.execute_async_script('return GaiaDataLayer.getAllVideos();')
[]
(Pdb) self.marionette.execute_async_script('return GaiaDataLayer.getAllMusic();')
False
(Pdb) self.marionette.execute_async_script('return GaiaDataLayer.getAllPictures();')
[]
`