Fix array_merge error and update exception handling

src/Prime/Notification/Envelope.php

@@ -175,7 +175,7 @@ final class Envelope implements NotificationInterface
 
         return [
             ...$this->notification->toArray(),
-            'metadata' => array_merge(...$stamps),
+            'metadata' => $stamps ? array_merge(...$stamps) : [],
         ];
     }
 

src/Prime/Stamp/IdStamp.php

@@ -19,7 +19,7 @@ final readonly class IdStamp implements PresentableStampInterface, StampInterfac
     {
         try {
             return bin2hex(random_bytes(16));
-        } catch (\Exception) {
+        } catch (\Random\RandomException) {
             return uniqid('', true);
         }
     }