Add some missing ForceDefaults

Helps non-patched flatbuffer implementations work

Change-Id: I15d74e6b8fe379d6e6fb1d066b17b14322e2cbfb
diff --git a/aos/events/logging/logfile_utils_test.cc b/aos/events/logging/logfile_utils_test.cc
index 8e29335..384772c 100644
--- a/aos/events/logging/logfile_utils_test.cc
+++ b/aos/events/logging/logfile_utils_test.cc
@@ -255,6 +255,7 @@
     const aos::FlatbufferDetachedBuffer<Configuration> &config,
     const std::string_view json) {
   flatbuffers::FlatBufferBuilder fbb;
+  fbb.ForceDefaults(true);
   flatbuffers::Offset<Configuration> config_offset =
       aos::CopyFlatBuffer(config, &fbb);
   LogFileHeader::Builder header_builder(fbb);
@@ -266,6 +267,7 @@
       JsonToFlatbuffer<LogFileHeader>(json));
   CHECK(header_updates.Verify());
   flatbuffers::FlatBufferBuilder fbb2;
+  fbb2.ForceDefaults(true);
   fbb2.FinishSizePrefixed(
       aos::MergeFlatBuffers(config_header, header_updates, &fbb2));
   return fbb2.Release();