From 8d50c79c9163f13a62f08f2f6296e2ff99ab903d Mon Sep 17 00:00:00 2001
From: Michael Griebling <sam@c-inspirations.com>
Date: Mon, 27 Feb 2023 08:11:26 -0500
Subject: [PATCH] Fixed crash on invalid syntax in curly braces.

---
 Sources/SwiftMath/MathRender/MTMathListBuilder.swift | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/Sources/SwiftMath/MathRender/MTMathListBuilder.swift b/Sources/SwiftMath/MathRender/MTMathListBuilder.swift
index 69a117d..ac3216b 100644
--- a/Sources/SwiftMath/MathRender/MTMathListBuilder.swift
+++ b/Sources/SwiftMath/MathRender/MTMathListBuilder.swift
@@ -226,11 +226,12 @@ public struct MTMathListBuilder {
                 continue
             } else if char == "{" {
                 // this puts us in a recursive routine, and sets oneCharOnly to false and no stop character
-                let subList = self.buildInternal(false, stopChar: "}")
-                prevAtom = subList!.atoms.last
-                list.append(subList)
-                if oneCharOnly {
-                    return list
+                if let subList = self.buildInternal(false, stopChar: "}") {
+                    prevAtom = subList.atoms.last
+                    list.append(subList)
+                    if oneCharOnly {
+                        return list
+                    }
                 }
                 continue
             } else if char == "}" {