Reject to send NANs from the drivetrain code

Signed-off-by: Austin Schuh <austin.linux@gmail.com>
Change-Id: I776bdc4ff0c31a94eb98e9af4dac33304f366a70
diff --git a/frc971/control_loops/drivetrain/line_follow_drivetrain.cc b/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
index ea20bd0..9823f0c 100644
--- a/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
+++ b/frc971/control_loops/drivetrain/line_follow_drivetrain.cc
@@ -284,6 +284,9 @@
   } else if (minU < -12.0) {
     U_ = U_ - U_.Ones() * (minU + 12.0);
   }
+  if (!U_.allFinite()) {
+    U_.setZero();
+  }
 }
 
 flatbuffers::Offset<LineFollowLogging> LineFollowDrivetrain::PopulateStatus(