Server GUI directory should default to "None" (not registered)

[softins]

I have just tried this code for the first time (in fact it was the code for #2427 I tried, which incorporates these changes), and compared with 3.8.2, using default empty ini files to ensure all defaults were used:

/usr/local/bin/Jamulus -s -i /tmp/x.ini
./Jamulus -s -p 22125 -i /tmp/y.ini

The 3.8.2 defaulted to "Not registered", with the "make my server public" checkbox unticked, which is good.

The newer version defaulted to registering with Any Genre 1, which I think is not good. The directory drop-down should default to "None", if not set in the command line or ini file, so that a new server does not register with a directory until the user asks it to.

Originally posted by @softins in #2199 (comment)

[pljones]

The old client did this (watch the console output):

• On start up, default to registered with Any Genre 1
• Read the genre from the inifile, default to Any Genre 1
• Read the registration state from the inifile, default to unregistered
• Update the registration state

The new client says:

• Read the custom directory from the inifile, default to not set
• Read the genre from the inifile, default to Any Genre 1
• Set the registration state

So defaulting to Any Genre 1 hasn't changed but the effect has.

This is why the checkbox was a "hack", in my view - it causes a problem as you don't actually know where the user wanted to register and, when you check the box, you're forced to register with Any Genre 1.

[softins]

Yes, not enabling the form items to select the directory until you had enabled it was a design error in the versions up to and including 3.8.2. Now that the enabling of registration has been subsumed into the directory selection, this gives us the opportunity to fix that error and prevent the server registering anywhere until the user has said where. That's what this PR does.