Elements are being pushed twice

[GiovanePS]

Description
If an <element> is outside a <complexType> element, it is pushed twice. Like the following example:

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema
	xmlns:xsd="http://www.w3.org/2001/XMLSchema"
	targetNamespace="http://example.com/schemas"
	xmlns:ak="http://example.com/schemas"
	elementFormDefault="qualified">

	<xsd:element name="SomeElement">
	</xsd:element>
	<xsd:simpleType name="SomeSimpleType">
		<xsd:restriction base="xsd:string" />
	</xsd:simpleType>
</xsd:schema>

Just look at the code of OnElement method to see that this is true.

Steps to reproduce the issue:

1. Copy the above XSD to a blank file (minimal.xsd)
2. Run xgen -l Go -i minimal.xsd

Describe the results you received:
With the xgen version at commit d0691b7, there is no difference in the output, but the problem is still there. It is just perceived after, for example, the changes made in #87 and #89. With those changes, this will be the output received:

// Code generated by xgen. DO NOT EDIT.

package schema

// SomeElement ...
type SomeElement string

// SomeSimpleType ...
type SomeSimpleType interface{}

Describe the results you expected:
And then, this will be the expected output:

// Code generated by xgen. DO NOT EDIT.

package schema

// SomeElement ...
type SomeElement *SomeElement

// SomeSimpleType ...
type SomeSimpleType string

Output of go version:

go version go1.24.0 linux/amd64

xgen version or commit ID:

xgen version: 0.1.0