FOSS gamedev and creative worlds

When i created creative server and i started to build automobile way in distance 300-400 blocks i saw is next:

I can say what i installed accidentally mod Moon Test but afterwards i noticed and disabled

Moontest might have disabled the engine's map generator to replace it by its own generator, and once you disabled it there were simply no map generator. To fix it, go to the world's directory, and open "map_meta.txt". You should find a line with "mg_name = singlenode" (if that's not singlenode, then i'm wrong…), replace "singlenode" by the map generator you used previously (v5, v6… I don't know), and save the file.
So unexplored places will generate again, but there will remain holes. Go in a hole and type "/deleteblocks here" and it will remove the air and then generate the land again.

I hope this will help you.