Mailer class name should not contain invalid characters

[jcheron]

From @gildonei
A little bug:

1. Add mailer class
2. Fill a name with space
3. Press Validate button (should be save button)
4. Result: OK and Error (image 1)
5. Will get an error when try to access mailer module again (image 2)

To access Mailer Module again, rename created file in project-folder/app/mail/"name with space".php to a name without space and, rename the className inside the file to remove spaces

see phpMv/ubiquity#56 (comment)