GitLab

CRWWebController removes WKWebView when the web process is evicted
(crbug/815248). This leaves WKBasedNavigationManager in an inconsistent
state as previous_item_index_ may not be -1, but GetItemCount() is 0.
This causes a crash in OnNavigationItemCommitted() when user starts a
new navigation by typing into the omnibox.

Fix the crash by guarding the pointer dereference with a nullptr check.

Bug: 797756
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ie553efbe7bb558a8af955ca6f64e2b8aea58aacd
Reviewed-on: https://chromium-review.googlesource.com/996436Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548250}