Changing kit device does not mark the kit for saving

When changing the device for a kit, the kit is sometimes not marked for saving (does not turn bold), and when clicking OK and then re-opening the Options dialog, the device is back to its previous setting.

It is somewhat inconsistent when reproducing, but with these steps it seems to happen quite regularly:

• Select a Kit
• Open the "Device type" combobox, but close it again without changing the value
• Change the "Device" to a different device
• Click OK
• Open the Options -> Kit page again, the device change is not saved

I can reproduce this with both a BlackBerry device as well as with a Generic Linux Device, in both the 2.7 branch (HEAD b6257ef7) and the master branch (HEAD 948d8d7b).