"Stream is closed" error, but program finishes executing correctly

I'm running a .NET Spark app for batch processing with a selection of GitHub projects data. My program runs as expected up through making a Spark Sql call:

```csharp
// ...Code creating spark session, reading into data frame, doing some sorting...
// Then move on to creating UDF, SQL call:
spark.Udf().Register("MyUDF", (date) => DateTest(date));
cleanedProjects.CreateOrReplaceTempView("dateView");
DataFrame dateDf = spark.Sql("SELECT *, MyUDF(dateView.updated_at) AS datebefore FROM dateView");
```

After the Sql query, I perform a Filter() and Drop() for some final processing:
```csharp
DataFrame filteredDates = dateDf.Filter(dateDf["datebefore"] == true);
filteredDates.Show();
filteredDates.Drop("datebefore").Show();
```

After I Show() each of these modified DataFrames, I get the error: `ProcessStream() failed with exception: System.ArgumentException: The stream is closed.` However, even with that error, both calls to Show() do execute successfully and see the correct output.

Why might I be receiving this error (twice)? Since I get the correct output, the error doesn't seem to be affecting anything?