Fix debug_values (wrong comparison vs. assignment operator)

library/rules_shipping_framework.php

@@ -916,7 +916,7 @@ class ShippingRule {
 			return $varname;
 		} elseif ($varname=='values') {
 			return $vals;
-		} elseif ($varname=='values_debug' || $varname='debug_values') {
+		} elseif ($varname=='values_debug' || $varname=='debug_values') {
 			$tmpvals = $vals;
 			unset($tmpvals['debug_cart']);
 			unset($tmpvals['debug_products']);