refuse to delete frozen definitions

live.lua

@@ -160,6 +160,10 @@ function live.run(buf)
     live.send_to_driver(json.encode(Live.filename))
   elseif cmd == 'DELETE' then
     local definition_name = buf:match('^%s*%S+%s+(%S+)')
+    if Live.frozen_definitions[definition_name] then
+      live.send_to_driver('ERROR definition '..definition_name..' is part of Freewheeling infrastructure and cannot be deleted.')
+      return
+    end
     if Live.filename[definition_name] then
       local index = table.find(Live.filenames_to_load, Live.filename[definition_name])
       table.remove(Live.filenames_to_load, index)