Unexpected exit

[Paulo Bardes]

I came about this weird behavior when comparing some test cases I wrote for a
little shell I made for a CS class. Here's the thing:

$ echo | echo $(sleep 5) # ^Z and then bg to reproduce

If you just let it run everything is fine, but the weird thing is when you stop
it and resume in background bash will quit when the command finishes. I'm not
sure whether thats a bug or if I'm missing something. Just in case I'm sharing
my findings...

System info:
Linux 4.4.5-1-ARCH x86_64 GNU/Linux
GNU bash, version 4.3.42(1)-release (x86_64-unknown-linux-gnu)

-- Paul