[DevTools] Fix nullptr in headless_shell

I submitted another fix yesterday
(https://chromium-review.googlesource.com/c/chromium/src/+/1620940)
but turns out this one
is deeper in the stack. Also more obvious though.

Bug: 965544,961299,958667,958666
Change-Id: I1af8b47818545f902905b025b1a4a8ee0f4f4cc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1622466
Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661880}
1 file changed