wifi: WifiConfigController: fix possible NPE in showSecurityFields

Bug: 64438040
Test: make RunSettingsRoboTests -j40 ROBOTEST_FILTER=WifiConfigControllerTest

Change-Id: I2ddc5c07a3c95cba91cef532dc2c84529146d100
diff --git a/src/com/android/settings/wifi/WifiConfigController.java b/src/com/android/settings/wifi/WifiConfigController.java
index 1aabe5c..5a3d426 100644
--- a/src/com/android/settings/wifi/WifiConfigController.java
+++ b/src/com/android/settings/wifi/WifiConfigController.java
@@ -851,7 +851,7 @@
             mEapIdentityView = (TextView) mView.findViewById(R.id.identity);
             mEapAnonymousView = (TextView) mView.findViewById(R.id.anonymous);
 
-            if (mAccessPoint.isCarrierAp()) {
+            if (mAccessPoint != null && mAccessPoint.isCarrierAp()) {
                 mEapMethodSpinner.setSelection(mAccessPoint.getCarrierApEapType());
             }