Fixes out of range bug in SimpleConditionTracker.

One of the unit tests was flaky because mStopAllLogMatcherIndex may
be greater than the size of eventMatcherValues, so we access an
element that is greater than the vector size.

Test: Check unit-tests still work. Flake is a bit hard to find.
Change-Id: Ib177cd0ae00bbe7aa6982c6ec31d9094253a9c10