Don't call id on nil

lib/gollum/markup.rb

@@ -14,7 +14,7 @@ module Gollum
       @wiki    = page.wiki
       @name    = page.filename
       @data    = page.text_data
-      @version = page.version.id
+      @version = page.version.id if page.version
       @format  = page.format
       @dir     = ::File.dirname(page.path)
       @tagmap  = {}

lib/gollum/page.rb

@@ -381,6 +381,7 @@ module Gollum
     #
     # Returns the Page or nil if none exists.
     def find_sub_page(name)
+      return nil unless self.version
       return nil if self.filename =~ /^_/
       name = "_#{name.to_s.capitalize}"
       return nil if page_match(name, self.filename)