Fix condition for determining potential kit stock

Author: edupulpillo

htdocs/product/composition/card.php

@@ -687,7 +687,7 @@
 						// Calculate how many full kits this component can support.
 						$possible_with_this = floor($value['stock'] / $value['nb']);
 						// Keep the smallest value across all components (the limiting factor).
-						if ($potential_kit_stock === null || $possible_with_this < $potential_kit_stock) {
+						if ($potential_kit_stock === 0 || $possible_with_this < $potential_kit_stock) {
 							$potential_kit_stock = $possible_with_this;
 						}
 					} else {