Update logic to build slider slice

Return null when slider getMax() <= getMin(), instead of force
build it to make it crash

Fixes: 132657278
Test: RunSettingsRoboTests
Change-Id: I9f3c078ae07522aa8f1cebdee3f73df2d014d6bb

tests/robotests/src/com/android/settings/testutils/FakeInvalidSliderController.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.settings.testutils;
+
+import android.content.Context;
+
+public class FakeInvalidSliderController extends FakeSliderController {
+
+    public FakeInvalidSliderController(Context context, String key) {
+        super(context, key);
+    }
+
+    @Override
+    public int getMax() {
+        // Return 0 to make it invalid
+        return 0;
+    }
+}