Use early returns rather than large if in Variable#taint_check

lib/liquid/variable.rb

@@ -107,7 +107,9 @@ module Liquid
     end
 
     def taint_check(context, obj)
-      if obj.tainted? && Template.taint_mode != :lax
+      return unless obj.tainted?
+      return if Template.taint_mode == :lax
+
       @markup =~ QuotedFragment
       name = Regexp.last_match(0)
 
@@ -123,5 +125,4 @@ module Liquid
       end
     end
   end
-  end
 end