unknown resolver null

I'm follwing [https://absaoss.github.io/spline/#step-by-step](spline) and trying to get understand this.
so i was able to get Spline up and running using docker-compose

as per the dicumentation [http://localhost:9090/]( Spline UI). and [http://localhost:8080/](server) is running.

so i tried to with below command

```
pyspark \
--packages za.co.absa.spline.agent.spark:spark-3.0-spline-agent-bundle_2.12:1.0.2 \
--conf "spark.sql.queryExecutionListeners=za.co.absa.spline.harvester.listener.SplineQueryExecutionListener" \
--conf "spark.spline.producer.url=http://localhost:8080/producer"
```

In the terminal i was able to see below error

```
:: problems summary ::
:::: ERRORS
unknown resolver null

:: USE VERBOSE OR DEBUG MESSAGE LEVEL FOR MORE DETAILS
:: retrieving :: org.apache.spark#spark-submit-parent-1bda6b26-985d-462f-b21b-9eb6a34a5555
confs: [default]
0 artifacts copied, 26 already retrieved (0kB/6ms)
23/02/06 17:15:28 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
```

then i tried below command to run small pyspark code

```
spark-submit \
--packages za.co.absa.spline.agent.spark:spark-3.0-spline-agent-bundle_2.12:1.0.2 \
--conf "spark.sql.queryExecutionListeners=za.co.absa.spline.harvester.listener.SplineQueryExecutionListener" \
--conf "spark.spline.producer.url=http://localhost:8080/producer" \
./schema.py`

```

the error **unknown resolver null** was there and but code executed successfully
but i can't see any output **http://localhost:9090/app/events/list** here

any suggestions ??