Go to the file D:\xampp\htdocs\wp4shop\wp-content\plugins\wp-basics\admin\classes\class.options_machine.php and change the line 229:
Wrong:
foreach ($value['options'] as $key => $option) {
if (!isset($multi_stored[$key])) {$multi_stored[$key] = '';}
$of_key_string = $value['id'] . '_' . $key;
$output .= '<input type="checkbox" class="checkbox of-input" name="'.$value['id'].'['.$key.']'.'" id="'. $of_key_string .'" value="1" '. checked($multi_stored[$key], 1, false) .' /><label class="multicheck" for="'. $of_key_string .'">'. $option .'</label><br />';
}
Good:
foreach ($value['options'] as $key => $option) {
//if (!isset($multi_stored[$key])) {$multi_stored[$key] = '';}
$of_key_string = $value['id'] . '_' . $key;
$output .= '<input type="checkbox" class="checkbox of-input" name="'.$value['id'].'['.$key.']'.'" id="'. $of_key_string .'" value="1" '. checked($multi_stored[$key], 1, false) .' /><label class="multicheck" for="'. $of_key_string .'">'. $option .'</label><br />';
}
Is better if you only comment it. Tell me if this solve the error please.