Partial revert.

Partial revertion to maintain code-style consistency (might reimplement the
change later, but need to think on it a bit more for now, as there are lot
of other places in the code which utilise the former code-style still).

Author: Maikuolan

src/Loader.php

@@ -314,7 +314,7 @@ public function __construct(
 
         /** Calculate and build various paths. */
         foreach (['CachePath', 'QuarantinePath', 'SignaturesPath'] as $Path) {
-            if (!${$Path}) {
+            if (!$$Path) {
                 if (!$VendorPath) {
                     continue;
                 }