Fix crash in car system ui.

Override repositionNavigationBar() in CarStatusBar
and setNavigationIconHints() in CarNavigationBarView
since they are not used  for vehicles.

Bug: 26301185
Change-Id: I1995a514301305bfd2eed64d5f43bc92a6658e15
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/car/CarStatusBar.java b/packages/SystemUI/src/com/android/systemui/statusbar/car/CarStatusBar.java
index a72b5d0..31631f8 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/car/CarStatusBar.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/car/CarStatusBar.java
@@ -57,4 +57,10 @@
         carNavBar.setActivityStarter(this);
         mNavigationBarView = carNavBar;
     }
+
+    @Override
+    protected void repositionNavigationBar() {
+        // The navigation bar for a vehicle will not need to be repositioned, as it is always
+        // set at the bottom.
+    }
 }