Null check before access display cutout

In the gesture pointer event listener, check the existence of display
before accessing the display cutout. When the system server crashes, the
display could become null. Accessing it will cause NPE and will
interrupt the system server restart and causing the entire device
crashes and reboot.

Test: build
Bug: 354298618
Flag: EXEMPT bugfix
Change-Id: I5444a24ba3d77d3018bc8864c2f72e7c19809962