Summary:
gcc 4.9 complains that erase(0) is ambiguous, and may be either string::erase(size_t)
or string::erase(iterator) (since iterator is "char*", and for historical
reasons 0 can be interpreted as a null char*).
Fix the code to explicitly indicate that it means the erase(size_t) version.
Test Plan: Confirmed that the code built successfully with gcc 4.9.
Reviewers: durham, mitrandir, ttung
Reviewed By: ttung
Subscribers: net-systems-diffs@, yogeshwer, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D3911252
Signature: t1:3911252:1474589551:688ecab4d59053dbdf7b48a062f248d8363e17f3
