try to avoid passing NULL to file_put_contents()

passing IncomingMailAttachment::$filePath access through IncomingMailAttachment::__get() appears to ensure NULL does not get passed to file_put_contents();

src/PhpImap/IncomingMailAttachment.php

@@ -115,7 +115,7 @@ public function saveToDisk() : bool
 			return false;
 		}
 
-		if (false === file_put_contents($this->filePath, $this->dataInfo->fetch())) {
+		if (false === file_put_contents($this->__get('filePath'), $this->dataInfo->fetch())) {
 			unset($this->filePath, $this->file_path);
 
 			return false;