Move the empty($cassetteName) Check Up

Acts as a gaurd so no `substr(...)` operations are performed on a null
and break things.

src/VCRTestListener.php

@@ -45,15 +45,15 @@ public function startTest(Test $test): void
         $parsed = self::parseDocBlock($docBlock, '@vcr');
         $cassetteName = array_pop($parsed);
 
+        if (empty($cassetteName)) {
+            return;
+        }
+
         // If the cassette name ends in .json, then use the JSON storage format
         if (substr($cassetteName, -5) === '.json') {
             VCR::configure()->setStorage('json');
         }
 
-        if (empty($cassetteName)) {
-            return;
-        }
-
         VCR::turnOn();
         VCR::insertCassette($cassetteName);
     }