Fix potential memory leak of FrameTracker

If begin and end invocations are at the same frame, the end vsync id
will be smaller than the begin vsync id, results in zero size jank info
array, the finish call will be missed as well, a leak happens.

Bug: 192140966
Test: atest FrameTrackerTest InteractionJankMonitorTest
Change-Id: I388558e60bdb84ad248a9afabe7776c4e6e67c57
3 files changed