Fix starting application without any docks

[jdtimmerman]

Addressing issue #92. When removing all docks and closing the application, i found the following value in my Friture.conf

[Docks]
Dock%201\timeRange=50
Dock%201\type=1
dockNames=@Invalid()

While i did not find a way to prevent the invalid value in the config file, i did find a way to handle the invalid one upon starting the application.

Tested on a linux system

[tlecomte]

Thank you very much @jdtimmerman, nice fix ! I'm merging it.