Merge "Do not create starting window if there is no task." into tm-dev

        // Attempt to add starting window from the top-most activity.

        for (int i = mDeferringAddStartActivities.size() - 1; i >= 0; --i) {

            final DeferringStartingWindowRecord next = mDeferringAddStartActivities.get(i);

            if (next.mDeferring.getTask() == null) {

                Slog.e(TAG, "No task exists: " + next.mDeferring.shortComponentName

                        + " parent: " + next.mDeferring.getParent());

                continue;

            }

            next.mDeferring.showStartingWindow(next.mPrev, mInitNewTask, mInitTaskSwitch,

                    mInitProcessRunning, true /* startActivity */, next.mSource, topOptions);

            // If one succeeds, it is done.