This reverts commit c2b5a8e6, reversing
changes made to 1918b12c.

See: https://github.com/rails/rails/pull/9660#issuecomment-27627493

Same as 4d4ff531

When the value for the required key is empty an ActionController::ParameterMissing is raised which gets caught by ActionController::Base and turned into a 400 Bad Request reply with a message in the body saying the key is missing, which is misleading.

With these changes, ActionController::EmptyParameter will be raised which ActionController::Base will catch and turn into a 400 Bad Request reply with a message in the body saying the key value is empty.

actionpack/lib/action_dispatch/middleware/exception_wrapper.rb:99: IO#lines is deprecated; use #each_line instead

Currently Rack raises a TypeError when it encounters a malformed or
ambiguous hash like `foo[]=bar&foo[4]=bar`. Rather than pass this
through to the application this commit captures the exception and
re-raises it using a new ActionController::BadRequest exception.

The new ActionController::BadRequest exception returns a 400 error
instead of the 500 error that would've been returned by the original
TypeError. This allows exception notification libraries to ignore
these errors if so desired.

Closes #3051

Raise a rescuable exception when Rails doesn't know what to do with the format, rather than responding with a head :not_acceptable (406)