fixed a printf format width in the indexer code
diff --git a/frc971/control_loops/index/index.cc b/frc971/control_loops/index/index.cc
index 72597c6..fd9b612 100644
--- a/frc971/control_loops/index/index.cc
+++ b/frc971/control_loops/index/index.cc
@@ -753,7 +753,7 @@
       case Goal::INTAKE:
         safe_goal_ = Goal::READY_SHOOTER;
         safe_to_change_state = false;
-        LOG(INFO, "We have %d discs, time to preload automatically\n",
+        LOG(INFO, "We have %"PRId32" discs, time to preload automatically\n",
             hopper_disc_count_);
         break;
       case Goal::READY_SHOOTER: