Fix native exception caused by memset 0 to NULL pointer

When memory is not enough, it will fail to allocate mSampleTimeEntries
and it will return NULL. So memset will set 0 to address 0x00, and
exception occurs.

Bug: 143057966
Test: this is a seldom issue and we analyze this exception by callstack
Change-Id: Ia69884a984c8d38e58b325b4043977e6e196e6a2