tree f1aa8bb15c1e2f237c476b3d441c455321fa3397
parent f72a86f8ac3ee46c5646d35678b17903d305c311
author Leon Senft <leonsenft@google.com> 1534276247 -0700
committer Leon Senft <leonsenft@users.noreply.github.com> 1534280592 -0700

Fix a crash caused by `:host()` without an argument

Parsing `:host()` without an argument now emits an error explaining that a
selector argument is expected, rather than crashing.