From a543eeb162cbb67fa68974d01cf295316cf6647f Mon Sep 17 00:00:00 2001
From: night199uk <night199uk@hermitcrabslab.com>
Date: Sat, 22 Dec 2018 08:12:27 +0100
Subject: [PATCH] Fix assert on empty options for a Rule

---
 lark/load_grammar.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 3c11830..a9de749 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -510,8 +510,7 @@ class Grammar:
 
                 empty_indices = [x==_EMPTY for i, x in enumerate(expansion)]
                 if any(empty_indices):
-                    assert options
-                    exp_options = copy(options)
+                    exp_options = copy(options) or RuleOptions()
                     exp_options.empty_indices = empty_indices
                     expansion = [x for x in expansion if x!=_EMPTY]
                 else: