Handle invalid empty args to createAutoBrightnessSpline

BUG: 18572096
Change-Id: I9dfc2215994a4f7a70ef6bdd04b620917e4ec034
diff --git a/services/core/java/com/android/server/display/DisplayPowerController.java b/services/core/java/com/android/server/display/DisplayPowerController.java
index 8f8afd5..61af8ed 100644
--- a/services/core/java/com/android/server/display/DisplayPowerController.java
+++ b/services/core/java/com/android/server/display/DisplayPowerController.java
@@ -1181,6 +1181,10 @@
     }
 
     private static Spline createAutoBrightnessSpline(int[] lux, int[] brightness) {
+        if (lux == null || lux.length == 0 || brightness == null || brightness.length == 0) {
+            Slog.e(TAG, "Could not create auto-brightness spline.");
+            return null;
+        }
         try {
             final int n = brightness.length;
             float[] x = new float[n];