Activate old iPhone 3G issue

Hello,

I have an old iPhone 3G that I want to use to play music with my Zeppelin.
It been working in the past but I wanted to install a radio app from the appstore and I got the message I hd to install newer firmware.

So I upgraded the firmware as I've been asked. Now since I don't have any sim card, I am stuck with the No sim card installed blahblah message in the iPhone screen.

Any way to activate it without any sim card at all? I just need the device to play music at home

thanks