fix environment detection in litesupport.rb after erb addition

Author: oldmoe

lib/litestack/litesupport.rb

@@ -15,7 +15,7 @@ class Error < StandardError; end
 
   # Detect the Rack or Rails environment.
   def self.detect_environment
-    if defined? Rails
+    if defined?(Rails) && Rails.respond_to?(:env)
       Rails.env
     elsif ENV["RACK_ENV"]
       ENV["RACK_ENV"]