Theme Wizard does not use the live screen's size as default when overwriting "Output Area Locations"

Hello,

1) Set you screen resolution to 1280x1024 (or anything but not 1024x768).
2) Start OpenLP
3) Create a new design or edit an existing one.
4) Go to the page "Output Area Locations"
5) Untick "Use default location"
6) Click "Layout Preview"

Result:
You see that the red and blue squares are either too small (not using the space they can) or they are too big (running of the screen).

Expected:
The combo boxes should be set to the values we are using when "Use default location" is enabled. (I think that the lyrics/footer locations should not be different when you enable/disable the check box.)

NOTE:
The screen size should be used as default, so when the user overrides the live display output size we should use this (and not the 2nd screen size).

Cheers