Improve failed to find boot message

Change-Id: I05cda7ff53b2a3355ca6c812dc5b0e02d33b356d
Signed-off-by: milind-u <milind.upadhyay@gmail.com>
diff --git a/aos/events/logging/log_namer.cc b/aos/events/logging/log_namer.cc
index a880f35..9830a61 100644
--- a/aos/events/logging/log_namer.cc
+++ b/aos/events/logging/log_namer.cc
@@ -107,9 +107,9 @@
     QueueHeader(MakeHeader());
   }
   CHECK_EQ(state_[node_index_].boot_uuid, source_node_boot_uuid);
+  CHECK(writer);
   CHECK(header_written_) << ": Attempting to write message before header to "
                          << writer->filename();
-  CHECK(writer);
   writer->QueueSizedFlatbuffer(fbb, now);
 }