I get booted back to GDM. This shows up in dmesg:
[29537.146563] gnome-shell[2971]: segfault at 0 ip 00007f82edaf25cf sp 00007ffea9697cb0 error 4 in libst-15.so[475cf,7f82edac8000+54000] likely on CPU 4 (core 0, socket 0)
[29537.146579] Code: 00 00 00 48 8b 44 24 10 49 83 ed 08 49 39 c5 0f 84 c9 02 00 00 48 8b 83 28 01 00 00 4c 89 e6 4a 8b 2c 28 48 8b 45 00 48 8b 00 <48> 8b 38 e8 a9 8b fd ff 41 89 c6 85 c0 75 ca 8b 05 3c 16 03 00 4c