Fix Android cleanup on gatt disconnect (#109)

android/src/main/kotlin/com/navideck/universal_ble/UniversalBleHelper.kt

@@ -178,9 +178,9 @@ fun <T> SparseArray<T>.toList(): List<Pair<Int, T>> {
 fun BluetoothGatt.getCharacteristic(
     service: String,
     characteristic: String,
-): BluetoothGattCharacteristic? =
-    getService(UUID.fromString(service)).getCharacteristic(UUID.fromString(characteristic))
-
+): BluetoothGattCharacteristic? {
+    return getService(UUID.fromString(service))?.getCharacteristic(UUID.fromString(characteristic))
+}
 
 fun subscriptionFailedError(error: String? = null): Result<Unit> {
     return Result.failure(

android/src/main/kotlin/com/navideck/universal_ble/UniversalBlePlugin.kt

@@ -716,7 +716,6 @@ class UniversalBlePlugin : UniversalBlePlatformChannel, BluetoothGattCallback(),
     private fun cleanConnection(gatt: BluetoothGatt) {
         knownGatts.remove(gatt)
         gatt.disconnect()
-        gatt.close()
 
         readResultFutureList.removeAll {
             if (it.deviceId == gatt.device.address) {
@@ -885,6 +884,8 @@ class UniversalBlePlugin : UniversalBlePlatformChannel, BluetoothGattCallback(),
                     gatt.device.address, false, status.parseHciErrorCode()
                 ) {}
             }
+            Log.d(TAG, "Closing gatt for ${gatt.device.name}")
+            gatt.close()
         }
     }