fix: Revert comparison with null

Author: neznaika0

system/Common.php

@@ -75,7 +75,7 @@ function cache(?string $key = null)
         $cache = service('cache');
 
         // No params - return cache object
-        if ((string) $key === '') {
+        if ($key === null) {
             return $cache;
         }
 
@@ -1128,7 +1128,7 @@ function timer(?string $name = null, ?callable $callable = null)
     {
         $timer = service('timer');
 
-        if ((string) $name === '') {
+        if ($name === null) {
             return $timer;
         }
 

tests/system/Email/EmailTest.php

@@ -55,7 +55,7 @@ public function testEmailSendWithClearance($autoClear): void
 
         $this->assertTrue($email->send($autoClear));
 
-        if ($autoClear) {
+        if (! $autoClear) {
             $this->assertSame('[email protected]', $email->archive['recipients'][0]);
         }
     }