Fixing crash when checking for home task resizeability.

- If there is no home task, assume non-resizeable until user goes
  home.

Bug: 62033711
Test: Reboot phone, launch settings from QS, dock and ensure no
      crash.  Go home and ensure that launcher is still resizeable
      and bounds are correct.

Change-Id: Id7ccd6f54cc4dc248f90a1acb54509713c69b11b
(cherry picked from commit f7fb5e39)