Don't exit REPL on OS button press when there are multiple views on the stack

Currently pressing the OS button while running an app through REPL makes the badge reboot.

It's better than having it on the app button like it was before, but still not ideal. When one launches apps that use multiple views via mpremote, trying to go back on the view stack leads to a reboot.

It would be nice if st3m was able to inhibit the reboot while an app is running and there are multiple views on the stack.