Fix assert_template_result tests not picking up Liquid::Environment.default.error_mode

The `rake test` command gave us the impression that we were running all the tests
on all the error modes, that was false.

lib/liquid/tags/cycle.rb

@@ -78,6 +78,7 @@ module Liquid
       # Parse remaining comma-separated expressions
       while p.consume?(:comma)
         break if p.look(:end_of_string)
+
         @variables << maybe_dup_lookup(safe_parse_expression(p))
       end