Call BluetoothGatt#close() after disconnecting

device/bluetooth/android/java/src/org/chromium/device/bluetooth/ChromeBluetoothRemoteGattCharacteristic.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.device.bluetooth;
 
 import android.annotation.TargetApi;
 import android.bluetooth.BluetoothGattCharacteristic;
 import android.bluetooth.BluetoothGattDescriptor;
 import android.os.Build;
@@ skipping 36 matching lines @@
 
         Log.v(TAG, "ChromeBluetoothRemoteGattCharacteristic created.");
     }
 
     /**
      * Handles C++ object being destroyed.
      */
     @CalledByNative
     private void onBluetoothRemoteGattCharacteristicAndroidDestruction() {
         Log.v(TAG, "ChromeBluetoothRemoteGattCharacteristic Destroyed.");
-        mChromeDevice.mBluetoothGatt.setCharacteristicNotification(mCharacteristic, false);
+        if (mChromeDevice.mBluetoothGatt != null) {
+            mChromeDevice.mBluetoothGatt.setCharacteristicNotification(mCharacteristic, false);
+        }
         mNativeBluetoothRemoteGattCharacteristicAndroid = 0;
         mChromeDevice.mWrapperToChromeCharacteristicsMap.remove(mCharacteristic);
     }
 
     void onCharacteristicChanged() {
         Log.i(TAG, "onCharacteristicChanged");
         if (mNativeBluetoothRemoteGattCharacteristicAndroid != 0) {
             nativeOnChanged(
                     mNativeBluetoothRemoteGattCharacteristicAndroid, mCharacteristic.getValue());
         }
@@ skipping 141 matching lines @@
 
     // Binds to BluetoothRemoteGattCharacteristicAndroid::OnWrite.
     native void nativeOnWrite(long nativeBluetoothRemoteGattCharacteristicAndroid, int status);
 
     // Binds to BluetoothRemoteGattCharacteristicAndroid::CreateGattRemoteDescriptor.
     // TODO(http://crbug.com/505554): Replace 'Object' with specific type when JNI fixed.
     private native void nativeCreateGattRemoteDescriptor(
             long nativeBluetoothRemoteGattCharacteristicAndroid, String instanceId,
             Object bluetoothGattDescriptorWrapper, Object chromeBluetoothDevice);
 }