[swarming] Be tolerant to inconsistent index
[swarming] Be tolerant to inconsistent index

This is to handle new logging code in d2a77d1006ed33d803e2292e15738b66e8944b24.

Bug: 884579
Change-Id: I7b688e3d489f0fe3c96eba6b7a90c438d7e5473a
Reviewed-on: https://chromium-review.googlesource.com/c/1363534
Reviewed-by: Quinten Yearsley <747cf52e0cef2e3e9371802a2d344b6c87126a4b@chromium.org>
Commit-Queue: Marc-Antoine Ruel <d2bf0fc09b08f7b0888b3ddab32b3e89c7122c8b@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py