fix: 修复低功耗蓝牙无法读取特征值数据的Bug

src/platforms/app-plus/service/api/device/bluetooth.js

@@ -134,6 +134,7 @@ export function notifyBLECharacteristicValueChanged (data, callbackId) {
 }
 
 export function readBLECharacteristicValue (data, callbackId) {
+  onBLECharacteristicValueChange = onBLECharacteristicValueChange || bluetoothOn('onBLECharacteristicValueChange')
   bluetoothExec('readBLECharacteristicValue', callbackId, data)
 }