An object is blank if it’s nil, empty, or a whitespace string. For example, "", " ", nil, [], and {} are blank.

This simplifies

if !address.nil? && !address.empty?

to

if !address.blank?

Source Code

# File action_mailer/vendor/tmail-1.1.0/tmail/core_extensions.rb, line 19
def blank?
  if respond_to?(:empty?) && respond_to?(:strip)
    empty? or strip.empty?
  elsif respond_to?(:empty?)
    empty?
  else
    !self
  end
end