This fixes the condition where the i3 socket for some reason did not produce an
error, but the X server exited (earlier than i3?) and the left-over i3bar
process would consume 100% CPU.
How to reproduce the problem:
1) Start ./testcases/Xdummy :8
2) Start DISPLAY=:8 i3bar -s <socket path to i3 on :0>
3) Kill the Xdummy
7064cfc2a0