Don't try to remove node from invalid network master

api.lua

@@ -514,6 +514,9 @@ end
 
 industrialtest.api.removeNodeFromNetwork=function(pos,nodePos)
 	local meta=minetest.get_meta(pos)
+	if not meta:contains("industrialtest.network") then
+		return
+	end
 	local network=minetest.deserialize(meta:get_string("industrialtest.network"))
 	local removed=false
 	for key,node in ipairs(network) do