Validate log file reading assumptions more aggressively.

Change-Id: Ia04eb146966ee5a33899721766f1aeb36688083c
diff --git a/aos/events/logging/logfile_utils.cc b/aos/events/logging/logfile_utils.cc
index 58e7c30..908e5e1 100644
--- a/aos/events/logging/logfile_utils.cc
+++ b/aos/events/logging/logfile_utils.cc
@@ -613,6 +613,7 @@
     // but we then want to find the next message to read.  The conservative
     // answer is to immediately trigger a second requeue to get things moving.
     time_to_queue_ = monotonic_start_time();
+    CHECK_NE(time_to_queue_, monotonic_clock::min_time);
     QueueMessages(time_to_queue_);
   }