Remove usage of CHECK_NOTNULL

We want to switch to absl logging instead of glog.  gtest and ceres are
going there, and we already have absl as a dependency.  ABSL doesn't
have CHECK_NOTNULL, and we can move things over in an easier to review
fashion.

Change-Id: Ifd9a11ec34a2357cec43f88dba015db9c28ed2cf
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2024/control_loops/drivetrain/drivetrain_base.cc b/y2024/control_loops/drivetrain/drivetrain_base.cc
index 79d35e1..dd4f33c 100644
--- a/y2024/control_loops/drivetrain/drivetrain_base.cc
+++ b/y2024/control_loops/drivetrain/drivetrain_base.cc
@@ -11,9 +11,10 @@
 const frc971::control_loops::drivetrain::DrivetrainConfig<double>
 GetDrivetrainConfig(aos::EventLoop *event_loop) {
   frc971::constants::ConstantsFetcher<Constants> constants_fetcher(event_loop);
+  CHECK(constants_fetcher.constants().common() != nullptr);
+  CHECK(constants_fetcher.constants().common()->drivetrain() != nullptr);
   return frc971::control_loops::drivetrain::DrivetrainConfig<double>::
-      FromFlatbuffer(
-          *CHECK_NOTNULL(constants_fetcher.constants().common()->drivetrain()));
+      FromFlatbuffer(*constants_fetcher.constants().common()->drivetrain());
 };
 
 }  // namespace y2024::control_loops::drivetrain