Ensure proper Actions handling when no tabs are available.

The origin of this scenario is somewhat unknown, but according to
the crash/ site, it is possible for the user to have an interactable
Omnibox that is not attached to a valid tab.

This change ensures we are always checking whether Tab is available
before evaluating if it is an incognito and/or interactable one.

Bug: 1465283
Change-Id: Id6dbe4349f1aff8e5e260ae1a5cd06634db43d72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4691325


Auto-Submit: Tomasz Wiszkowski <ender@google.com>
Reviewed-by: Fred Mello <fredmello@chromium.org>
Commit-Queue: Tomasz Wiszkowski <ender@google.com>
Cr-Commit-Position: refs/heads/main@{#1171404}