plugin sub page error

<?php

//call register settings function
function register_mysettings() {
    //register our settings
    register_setting( 'wpg-settings-group', 'customfooter' );
    register_setting( 'wpg-settings-group', 'removepostssec' );
    register_setting( 'wpg-settings-group', 'removemediasec' );
}
add_action( 'admin_init', 'register_mysettings' );





function remove_menus () {
if (get_option('removepostssec') != NULL ) {
remove_menu_page( 'edit.php' ); } // Posts

if (get_option('removemediasec') != NULL ) {
remove_menu_page( 'upload.php' ); } // Media

if (get_option('removepagessec') != NULL ) {
remove_menu_page( 'edit.php?post_type=page' ); } // Pages

if (get_option('removelinkssec') != NULL ) {
remove_menu_page( 'link-manager.php' ); }// Links

}
add_action('admin_menu', 'remove_menus');



function modify_footer_admin () {
  echo get_option('customfooter');
  echo 'Powered by<a href="http://WordPress.org">WordPress</a>.';
}
add_filter('admin_footer_text', 'modify_footer_admin');

?>
<div class="wrap">
<form method="post" action="options.php">
    <?php settings_fields( 'wpg-settings-group' ); ?>
    <table class="form-table">
        <tr valign="top">
        <th scope="row">Enable custom footer text? </th>
        <td><input type="text" name="customfooter" value="<?php echo get_option('customfooter'); ?>" /></td></tr>
        <tr><th scope="row">Remove Posts section?</th>
        <td>
        <?php
    echo '<input name="removepostssec" id="gv_thumbnails_insert_into_excerpt" type="checkbox" value="1" class="code" ' . checked( 1, get_option('removepostssec'), false ) . ' /> Yes'; ?>
        </td>
        </tr>
        <tr><th scope="row">Remove Posts section?</th>
        <td>
        <?php
    echo '<input name="removemediasec" id="gv_thumbnails_insert_into_excerpt" type="checkbox" value="1" class="code" ' . checked( 1, get_option('removemediasec'), false ) . ' /> Yes'; ?>
        </td>
        </tr>

    </table>


        <p class="submit">
            <input name="Submit" type="submit" class="button-primary" value="<?php esc_attr_e('Save Changes'); ?>" />
        </p>
        </form>

</form>
</div>