Don't crash the wizard if tvh has no inputs

Don't crash the wizard if tvh has no inputs

If you have e.g. all but dvb disabled and forgot to plug in your usb
adapter the wizard would crash upon you as no inputs are defined and the
looping assumes there is at least one. Ideally a message should be shown
to indicate that you need inputs, but a wizard displaying a mostly empty
page is far better than a crash to discover your mistake.