Check null values explicitly in Arrow writing

Author: Kopilov

dataframe-arrow/src/main/kotlin/org/jetbrains/kotlinx/dataframe/io/ArrowWriterImpl.kt

@@ -249,7 +249,7 @@ internal class ArrowWriterImpl(
         strictType: Boolean,
         strictNullable: Boolean,
     ): FieldVector {
-        val containNulls = (column == null || column.hasNulls())
+        val containNulls = (column == null || column.values().any { it == null})
         // Convert the column to type specified in field. (If we already have target type, convertTo will do nothing)
 
         val (convertedColumn, actualField) = try {