Quiet up LogReader when messages aren't available

We were printing the whole contents.  This is slow and not very helpful.
Strip out big vectors.

Change-Id: I40af22e79fb62c39f277271a88a24488d4afa7d7
diff --git a/aos/events/logging/logger.cc b/aos/events/logging/logger.cc
index 7d0040c..51150a3 100644
--- a/aos/events/logging/logger.cc
+++ b/aos/events/logging/logger.cc
@@ -1390,7 +1390,9 @@
           << "Not sending data from before the start of the log file. "
           << channel_timestamp.monotonic_event_time.time_since_epoch().count()
           << " start " << monotonic_start_time().time_since_epoch().count()
-          << " " << FlatbufferToJson(channel_data);
+          << " "
+          << FlatbufferToJson(channel_data,
+                              {.multi_line = false, .max_vector_size = 100});
     }
 
     const monotonic_clock::time_point next_time = state->OldestMessageTime();