[ALPS05390740] ION: add handle valid check

add handle valid check to prevent invalid pointer dereference.

MTK-Commit-Id: 4e2d7eaf06c1cb4b63c87bfa6bce58f99a8cb643

Change-Id: I73f928d6bcc5640f8be3f8642aae43a5202950c4
Signed-off-by: Guangming Cao <Guangming.Cao@mediatek.com>
CR-Id: ALPS05390740
Feature: ION
(cherry picked from commit 3579e0fc6b43d06f962121d0f87007cb536937b3)