AC-11970: Imposible to reorder configurable products with one checkbox selected custom option

Author: wip44850

app/code/Magento/Catalog/Model/Product/Option/Type/Select.php

@@ -90,9 +90,7 @@ public function validateUserValue($values)
             }
         } else {
             if (!$this->_isSingleSelection()) {
-                if (is_string($value)) {
-                    $value = explode(',', $value);
-                }
+                $value = is_string($value) ? explode(',', $value) : [$value];
                 $valuesCollection = $option->getOptionValuesByOptionId($value, $this->getProduct()->getStoreId());
                 $valueCount = is_array($value) ? count($value) : 0;
                 if ($valuesCollection->count() != $valueCount) {