android.content.Context.sendBroadcast(android.content.Intent) on a null object reference

Attempt to invoke virtual method 'void android.content.Context.sendBroadcast(android.content.Intent)
on a null object reference
在Activity中我们一般是可以直接通过sendBroadcast(android.content.Intent)来发送广播的，但有时会出现如下的异常：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.content.Context.sendBroadcast(android.content.Intent)' on a null object reference
        at android.content.ContextWrapper.sendBroadcast(ContextWrapper.java:376)
        at com.znewsham.skiday.adapters.BluetoothLeService.broadcastUpdate(BluetoothLeService.java:152)
        at com.znewsham.skiday.adapters.BluetoothLeService.access$100(BluetoothLeService.java:50)
        at com.znewsham.skiday.adapters.BluetoothLeService$1.onServicesDiscovered(BluetoothLeService.java:118)
        at android.bluetooth.BluetoothGatt$1.onSearchComplete(BluetoothGatt.java:304)
        at android.bluetooth.IBluetoothGattCallback$Stub.onTransact(IBluetoothGattCallback.java:217)
        at android.os.Binder.execTransact(Binder.java:454)

I’m pretty stumped, and I’m not even sure that how to fix this issue to resolve my problems