omit -pass option in decrypt command if --password-file not given

lib/backup/cli/utility.rb

@@ -173,7 +173,7 @@ def decrypt
         case options[:encryptor].downcase
         when 'openssl'
           base64   = options[:base64] ? '-base64' : ''
-          password = options[:password_file] ? "-pass file:#{options[:password_file]}" : ''
+          password = options[:password_file].empty? ? '' : "-pass file:#{options[:password_file]}"
           salt     = options[:salt] ? '-salt' : ''
           %x[openssl aes-256-cbc -d #{base64} #{password} #{salt} -in '#{options[:in]}' -out '#{options[:out]}']
         when 'gpg'
@@ -224,7 +224,7 @@ def dependencies
           puts "Please wait..\n\n"
           puts %x[gem install #{options[:install]} -v '#{Backup::Dependency.all[options[:install]][:version]}']
         end
-        
+
         if options[:installed]
           puts %x[gem list -i -v '#{Backup::Dependency.all[options[:installed]][:version]}' #{options[:installed]}]
         end

spec/cli/utility_spec.rb

@@ -305,6 +305,19 @@
 #      cli.start
 #    end
 #
+#    it 'should omit -pass option if no --password-file given' do
+#      ARGV.replace(['decrypt', '--encryptor', 'openssl',
+#                    '--in', 'in_file',
+#                    '--out', 'out_file',
+#                    '--base64', '--salt'])
+#
+#      cli.any_instance.expects(:`).with(
+#        "openssl aes-256-cbc -d -base64  -salt " +
+#        "-in 'in_file' -out 'out_file'"
+#      )
+#      cli.start
+#    end
+#
 #    it 'should perform GnuPG decryption' do
 #      ARGV.replace(['decrypt', '--encryptor', 'gpg',
 #                    '--in', 'in_file',