Add null bytes to BLOB test data

Update test_scalar_function_blob_return_type to use \x00 (null bytes)
in test data, similar to test_append_blob pattern.

Author: suketa

test/duckdb_test/scalar_function_test.rb

@@ -235,7 +235,7 @@ def test_scalar_function_varchar_return_type # rubocop:disable Metrics/MethodLen
     def test_scalar_function_blob_return_type # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
       @con.execute('SET threads=1')
       @con.execute('CREATE TABLE test_table (data BLOB)')
-      @con.execute("INSERT INTO test_table VALUES ('\\x01\\x02\\x03'::BLOB), ('\\xAA\\xBB\\xCC'::BLOB)")
+      @con.execute("INSERT INTO test_table VALUES ('\\x00\\x01\\x02\\x03'::BLOB), ('\\x00\\xAA\\xBB\\xCC'::BLOB)")
 
       sf = DuckDB::ScalarFunction.new
       sf.name = 'add_prefix'
@@ -248,8 +248,8 @@ def test_scalar_function_blob_return_type # rubocop:disable Metrics/AbcSize, Met
       rows = result.to_a
 
       assert_equal 2, rows.size
-      assert_equal "\xFF\x01\x02\x03".b, rows[0][0]
-      assert_equal "\xFF\xAA\xBB\xCC".b, rows[1][0]
+      assert_equal "\xFF\x00\x01\x02\x03".b, rows[0][0]
+      assert_equal "\xFF\x00\xAA\xBB\xCC".b, rows[1][0]
     end
   end
 end