From a6832e09f4ddd77729f05372fbd84974fb79cfb6 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Sat, 5 Aug 2017 15:59:49 -0700
Subject: [PATCH] Fix mismatched parentheses causing exceptions.

---
 src/main/java/org/nwapw/abacus/parsing/ShuntingYardParser.java | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/main/java/org/nwapw/abacus/parsing/ShuntingYardParser.java b/src/main/java/org/nwapw/abacus/parsing/ShuntingYardParser.java
index 6239ed9..e6e930d 100644
--- a/src/main/java/org/nwapw/abacus/parsing/ShuntingYardParser.java
+++ b/src/main/java/org/nwapw/abacus/parsing/ShuntingYardParser.java
@@ -162,6 +162,7 @@ public class ShuntingYardParser implements Parser<Match<TokenType>>, PluginListe
     @Override
     public TreeNode constructTree(List<Match<TokenType>> tokens) {
         tokens = intoPostfix(new ArrayList<>(tokens));
+        if(tokens == null) return null;
         Collections.reverse(tokens);
         return constructRecursive(tokens);
     }