Producer fixes for fixed size list

Author: martin-traverse

adapter/avro/src/main/java/org/apache/arrow/adapter/avro/producers/AvroFixedSizeListProducer.java

@@ -51,7 +51,12 @@ public void produce(Encoder encoder) throws IOException {
     currentIndex++;
   }
 
-  // Do not override skipNull(), the delegate delegate vector will not hold data
+  @Override
+  public void skipNull() {
+    // Keep fixed sized child in sync
+    delegate.skipNull();
+    super.skipNull();
+  }
 
   @Override
   public void setPosition(int index) {

adapter/avro/src/main/java/org/apache/arrow/adapter/avro/producers/AvroListProducer.java

@@ -53,7 +53,7 @@ public void produce(Encoder encoder) throws IOException {
     currentIndex++;
   }
 
-  // Do not override skipNull(), the delegate delegate vector will not hold data
+  // Do not override skipNull(), delegate will not have an entry if the list is null
 
   @Override
   public void setPosition(int index) {

adapter/avro/src/main/java/org/apache/arrow/adapter/avro/producers/AvroNullableProducer.java

@@ -51,9 +51,9 @@ public void produce(Encoder encoder) throws IOException {
 
   @Override
   public void skipNull() {
-    // Should never be called on nullable producer
-    // Calling produce() will skipNull() on the delegate
-    throw new UnsupportedOperationException();
+    // Can be called by containers of nullable types
+    delegate.skipNull();
+    currentIndex++;
   }
 
   @Override