Exit with error if vports do not exist for any reason (#618)

Make sure node is registered before attempting to access the vports

mesecons_luacontroller/init.lua

@@ -470,7 +470,12 @@ local safe_globals = {
 
 local function create_environment(pos, mem, event, itbl, send_warning)
 	-- Gather variables for the environment
-	local vports = minetest.registered_nodes[minetest.get_node(pos).name].virtual_portstates
+	local node_def = minetest.registered_nodes[minetest.get_node(pos).name]
+	if not node_def then return end
+
+	local vports = node_def.virtual_portstates
+	if not vports then return end
+
 	local vports_copy = {}
 	for k, v in pairs(vports) do vports_copy[k] = v end
 	local rports = get_real_port_states(pos)
@@ -627,6 +632,7 @@ local function run_inner(pos, code, event)
 	-- Create environment
 	local itbl = {}
 	local env = create_environment(pos, mem, event, itbl, send_warning)
+	if not env then return false, "Env does not exist. Controller has been moved?" end
 
 	local success, msg
 	-- Create the sandbox and execute code