Fix writing null to a large list.

Author: Giorgi

DuckDB.NET.Data/Internal/Writer/ListVectorDataWriter.cs

@@ -140,6 +140,6 @@ private void ResizeVector(int rowIndex, ulong count)
             throw new DuckDBException($"Failed to reserve {vectorReservedSize} for the list vector");
         }
 
-        listItemWriter.FetchDataPointer();
+        listItemWriter.InitializerWriter();
     }
 }

DuckDB.NET.Data/Internal/Writer/VectorDataWriterBase.cs

@@ -109,8 +109,9 @@ internal unsafe bool AppendValueInternal<T>(T value, int rowIndex) where T : unm
         return true;
     }
 
-    internal void FetchDataPointer()
+    internal void InitializerWriter()
     {
+        validity = default;
         vectorData = NativeMethods.Vectors.DuckDBVectorGetData(Vector);
     }
 }

DuckDB.NET.Test/DuckDBManagedAppenderListTests.cs

@@ -137,7 +137,7 @@ public void ListValuesNullableDouble()
 
     private void ListValuesInternal<T>(string typeName, Func<Faker, T> generator, int? length = null)
     {
-        var rows = 10;
+        var rows = 2000;
         var table = $"managedAppenderLists";
 
         var columnLength = length.HasValue ? length.Value.ToString() : "";