fix read of 8192 bytes failed with errno=21 Is a directory

[remicollet]

With 7.4.0RC3

There was 1 error:
1) ZendTest\Mail\Storage\MboxFolderTest::testChangeFolderUnselectable
fgets(): read of 8192 bytes failed with errno=21 Is a directory
/builddir/build/BUILDROOT/php-zendframework-zend-mail-2.10.0-5.fc32.noarch/usr/share/php/Zend/Mail/Storage/Mbox.php:232
/builddir/build/BUILDROOT/php-zendframework-zend-mail-2.10.0-5.fc32.noarch/usr/share/php/Zend/Mail/Storage/Mbox.php:268
/builddir/build/BUILDROOT/php-zendframework-zend-mail-2.10.0-5.fc32.noarch/usr/share/php/Zend/Mail/Storage/Folder/Mbox.php:164
/builddir/build/BUILD/zend-mail-d7beb63d5f7144a21ac100072c453e63860cdab8/test/Storage/MboxFolderTest.php:143

This is a trivial fix which "also" mute E_NOTICE raised by fgets

[weierophinney]

This repository has been closed and moved to laminas/laminas-mail; a new issue has been opened at laminas/laminas-mail#7.

[weierophinney]

This repository has been moved to laminas/laminas-mail. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone laminas/laminas-mail to another directory.
• Copy the files from the second bullet point to the clone of laminas/laminas-mail.
• In your clone of laminas/laminas-mail, commit the files, push to your fork, and open the new PR.
  We will be providing tooling via laminas/laminas-migration soon to help automate the process.