PHP Notice: Trying to get property of non-object

Good afternoon,

This theme is giving me the above error on the file class_Admin.php

line 21:
// REMOVE PASSWORD FROM ADMIN
if( !current_user_can( ‘edit_user’, $userdata->ID ) ) {
add_filter( ‘show_password_fields’, ‘__return_false’ );
}
line 427:
// SWITCH PAGES
if(isset($_GET[‘page’]) && user_can($userdata->ID, ‘administrator’) ){

Line 500:
// ON THEME OVERVIEW PAGE
if ( user_can($userdata->ID, ‘administrator’) && $pagenow == ‘themes.php’ ) {
$this->UPDATECHILDTHEME();
}

Line 520:

// FIX FOR ADMIN QUERY
if (strpos(strtolower($_SERVER[‘REQUEST_URI’]), ‘/wp-admin’) !== false && $userdata->ID) {

And class_core.php

Line 9332:

if(is_numeric($id)){ $checkID = $id; }else{ $checkID = $post->ID; }

These warnings appear every day, is there any way to sort them out? Maybe a theme update?

Thanks,

Oscar