Quick fix to a bug that makes it possible to raise water levels everywhere with one source

src/map.cpp

@@ -1683,6 +1683,8 @@ void Map::transformLiquids(core::map<v3s16, MapBlock*> & modified_blocks)
 					if (nodemgr->getId(nodemgr->get(nb.n).liquid_alternative_flowing) != liquid_kind) {
 						neutrals[num_neutrals++] = nb;
 					} else {
+						// Do not count bottom source, it will screw things up
+						if(dirs[i].Y != -1)
 							sources[num_sources++] = nb;
 					}
 					break;