From 540f95c0f86950588eded5290cf623ba95376e5d Mon Sep 17 00:00:00 2001
From: Arne Keller <arne.keller@student.kit.edu>
Date: Sun, 29 Aug 2021 15:59:42 +0200
Subject: [PATCH] Fix NPE in frontend

---
 frontend/src/mathjax-proof-tree.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/frontend/src/mathjax-proof-tree.ts b/frontend/src/mathjax-proof-tree.ts
index c215776..e1442bb 100644
--- a/frontend/src/mathjax-proof-tree.ts
+++ b/frontend/src/mathjax-proof-tree.ts
@@ -374,7 +374,8 @@ class MathjaxProofTree extends MathjaxAdapter {
             const handleMouseEvent = (e: MouseEvent, mouseIn: boolean) => {
                 let typeTarget = e.target! as SVGGraphicsElement;
                 let counter = 0;
-                while (!typeTarget.classList.contains("typicalc-type")
+                while (typeTarget.classList
+                && !typeTarget.classList.contains("typicalc-type")
                 && !typeTarget.classList.contains("typicalc-label")) {
                     typeTarget = typeTarget.parentNode! as SVGGraphicsElement;
                     counter++;
@@ -382,6 +383,9 @@ class MathjaxProofTree extends MathjaxAdapter {
                         return;
                     }
                 }
+                if (!typeTarget.classList) {
+                    return;
+                }
                 let isType = typeTarget.classList.contains("typicalc-type");
                 let isLabel = typeTarget.classList.contains("typicalc-label");
                 if (mouseIn) {