Fixed SEGV that could happen if an exception is thrown during bootstrapping.
Fixed SEGV that could happen if an exception is thrown during bootstrapping.

BUG=chromium:487974
LOG=N

Review URL: https://codereview.chromium.org/1145703002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28453}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh