[zendframework/zf2#3571] wrote test
[zendframework/zf2#3571] wrote test

- Created test that demonstrates empty subject header is correctly
  parsed

matbech/zend-mail,stefanotorresi/zend-mail,MadCat34/zend-mail,rapidsoft-de/zend-mail,mleko/zend-mail,Xerkus/zend-mail,basz/zend-mail