Kazam's screencast automatic file saving directory settings always fallbacks to ~/Video after relaunch

[Ｖ字龍(Vdragon)]

As summary. The screenshot saving directory is not affected.

## Reproduce steps
1. Launch Kazam, open preference window
2. Change screencast saving directory to non-default and close the preference window
3. Open the preference window again.

## Known affected versions
kazam 1.4.4-1 from Ubuntu 14.04LTS repo
kazam 1.5.0 from ppa:kazam-team/unstable-series

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: kazam 1.4.4-1
Uname: Linux 3.15.0-031500rc7-lowlatency x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: KDE
Date: Wed Jul 23 18:32:53 2014
ExecutablePath: /usr/bin/kazam
InstallationDate: Installed on 2013-01-26 (542 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130126)
InterpreterPath: /usr/bin/python3.4
PackageArchitecture: all
SourcePackage: kazam
UpgradeStatus: Upgraded to trusty on 2014-04-21 (92 days ago)