Improper saluation handling for test send

[zopyx]

The salutation handling code is broken for test send:

https://github.com/collective/Products.EasyNewsletter/blob/master/Products/EasyNewsletter/content/ENLIssue.py#L378-L389

(Pdb) salutation_mappings
{'ms': {'de': 'Sehr geehrte Damen und Herren,'}, 'mr': {'de': 'Sehr geehrte Damen und Herren,'}}


(Pdb) salutation = salutation_mappings.get('default', '')
(Pdb) salutation
''
(Pdb) salutation.get(self.Language(), '')
*** AttributeError: 'str' object has no attribute 'get'

[zopyx]

The same issue is true for the real send operation.