Fix NoMethodError for start_with

Author: hsbt

lib/rdoc/store.rb

@@ -975,7 +975,7 @@ def marshal_load(file)
     case obj
     when true, false, nil, Array, Class, Encoding, Hash, Integer, String, Symbol, RDoc::Text
     else
-      unless obj.class.name.start_with("RDoc::")
+      unless obj.class.name.start_with?("RDoc::")
         raise TypeError, "not permitted class: #{obj.class.name}"
       end
     end