Don't set background color if TDA doesn't have a valid surface

This is something that sometimes occurs in tests since the detaching of the TDA in not necesseraily synchronized with animations

Test: atest CtsWindowManagerDeviceTestCases:MultiDisplaySystemDecorationTests
Bug: 207667555
Bug: 209936970
Merged-In: I9881453ba14cba4f219861ec4449f2baa8058b57
Change-Id: I9881453ba14cba4f219861ec4449f2baa8058b57
(cherry picked from commit e644ff61)