Fix file sending, as a result of moving $size into Send::class when optimising mail sending

app/Classes/File/Send/Dynamic.php

@@ -46,9 +46,6 @@ final class Dynamic extends Send
 			case 'mtime':
 				return $this->sent->timestamp;
 
-			case 'size':
-				return strlen($this->buffer);
-
 			default:
 				return NULL;
 		}
@@ -104,6 +101,7 @@ final class Dynamic extends Send
 	public function open(string $compress=''): bool
 	{
 		$this->buffer = (string)$this->item;
+		$this->size = strlen($this->buffer);
 
 		return TRUE;
 	}