Fix condition for String#encode!

[chulkilee]

No description provided.

[macournoyer]

This doesn't seem to be required. What error do you get and what Ruby version?

[chulkilee]

It is required because the existence of encode! does not necessary mean the existence of Encoding class.

Maybe it would be better to check ruby version >= 1.9, but I do not know much about different ruby implementation, so made the minimum change (which is enough).

It is happening when I use Rails 3 action mailer with ruby 1.8.7 - I added String#encode! which does nothing. In this case, Thin raises errors (unknown class Encoding). See ActionMailer 3 error - undefined method `encode!' for “Welcome”:String for the reference.

[macournoyer]

Hmm. Might as well just check w/ if defined?(Encoding). Drop the respond_to.