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 f7fb5e39882eb73ec46c21cfcd088a350fd5a99b)
diff --git a/services/core/java/com/android/server/wm/TaskStack.java b/services/core/java/com/android/server/wm/TaskStack.java
index 9d48ce5..d189ff8 100644
--- a/services/core/java/com/android/server/wm/TaskStack.java
+++ b/services/core/java/com/android/server/wm/TaskStack.java
@@ -738,7 +738,8 @@
 
         // When the home stack is resizable, should always have the same stack and task bounds
         if (mStackId == HOME_STACK_ID) {
-            if (findHomeTask().isResizeable()) {
+            final Task homeTask = findHomeTask();
+            if (homeTask != null && homeTask.isResizeable()) {
                 // Calculate the home stack bounds when in docked mode and the home stack is
                 // resizeable.
                 getDisplayContent().mDividerControllerLocked