JB_MR1: native/libs/ui: Adding fix for conf 2.0 seg faults

function call to cancelBuffer was resulted in seg-faults on conf 2.0.
Setting function pointer of cancelBuffer to null in order to select
correct path of execution.
CRs-fixed: 383715

Change-Id: I6de8355febaea86ded63f33a582c787fef862193