MINOR: [Go] check nil buffer in SizeInBytes (#42227)

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### Rationale for this change


![image](https://github.com/apache/arrow/assets/86254270/15265fff-03b3-4c8a-9599-a07675eb1e60)

Saw a nil error. Unclear to me how this nil buffer got constructed,
because when building the arrow data we seem to already check it. But we
should do a nil check here anyway

### What changes are included in this PR?

Added a nil check. 

### Are these changes tested?

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### Are there any user-facing changes?

No.

---------

Co-authored-by: Matt Topol <[email protected]>

go/arrow/array/data.go

@@ -201,7 +201,9 @@ func (d *Data) SizeInBytes() uint64 {
 	}
 
 	for _, b := range d.Buffers() {
-		size += uint64(b.Len())
+		if b != nil {
+			size += uint64(b.Len())
+		}
 	}
 	for _, c := range d.Children() {
 		size += c.SizeInBytes()

go/arrow/array/data_test.go

@@ -17,6 +17,7 @@
 package array
 
 import (
+	"slices"
 	"testing"
 
 	"github.com/apache/arrow/go/v17/arrow"
@@ -60,6 +61,17 @@ func TestSizeInBytes(t *testing.T) {
 	var arrayData arrow.ArrayData = data
 	dataWithChild := NewData(&arrow.StringType{}, 10, buffers1, []arrow.ArrayData{arrayData}, 0, 0)
 
+	buffers2 := slices.Clone(buffers1)
+	buffers2[0] = nil
+	dataWithNilBuffer := NewData(&arrow.StringType{}, 10, buffers2, nil, 0, 0)
+
+	t.Run("nil buffers", func(t *testing.T) {
+		expectedSize := uint64(30)
+		if actualSize := dataWithNilBuffer.SizeInBytes(); actualSize != expectedSize {
+			t.Errorf("expected size %d, got %d", expectedSize, actualSize)
+		}
+	})
+
 	t.Run("buffers only", func(t *testing.T) {
 		expectedSize := uint64(45)
 		if actualSize := data.SizeInBytes(); actualSize != expectedSize {