Merge branch 'hotfix/84'

Close #84

Author: michalbundyra

CHANGELOG.md

@@ -24,6 +24,8 @@ All notable changes to this project will be documented in this file, in reverse
 
 - [#83](https://github.com/laminas/laminas-mail/pull/83) fixes PHPDocs in `Transport\InMemory` (last message can be `null`).
 
+- [#84](https://github.com/laminas/laminas-mail/pull/84) fixes PHP 7.4 compatibility.
+
 ## 2.10.0 - 2018-06-07
 
 ### Added

src/Storage/Mbox.php

@@ -257,6 +257,10 @@ protected function openMboxFile($filename)
             $this->close();
         }
 
+        if (is_dir($filename)) {
+            throw new Exception\InvalidArgumentException('file is not a valid mbox file');
+        }
+
         ErrorHandler::start();
         $this->fh = fopen($filename, 'r');
         $error = ErrorHandler::stop();