Add null pointer check for addLockoutResetCallback

Fixes: 155988975

Test: Follow steps in comment#3, no system_server crash
Change-Id: Ie138286efe5c08ddc98cc74a034558ec43d5cf35

services/core/java/com/android/server/biometrics/BiometricServiceBase.java

@@ -978,6 +978,10 @@ public abstract class BiometricServiceBase extends SystemService
     }
 
     protected void addLockoutResetCallback(IBiometricServiceLockoutResetCallback callback) {
+        if (callback == null) {
+            Slog.w(getTag(), "Null LockoutResetCallback");
+            return;
+        }
         mHandler.post(() -> {
            final LockoutResetMonitor monitor = new LockoutResetMonitor(callback);
            if (!mLockoutMonitors.contains(monitor)) {