From d475b19e9ba7bc8870ec7bc1e10b5cc88decea0b Mon Sep 17 00:00:00 2001
From: Tyler Schicke <tyler_schicke@brown.edu>
Date: Mon, 24 Jun 2019 15:56:42 -0400
Subject: fixed crash

---
 src/new_fields/util.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/new_fields/util.ts b/src/new_fields/util.ts
index cadd8f8d0..abb777adf 100644
--- a/src/new_fields/util.ts
+++ b/src/new_fields/util.ts
@@ -21,7 +21,9 @@ const _setterImpl = action(function (target: any, prop: string | symbol | number
         target[prop] = value;
         return true;
     }
-    value = value[SelfProxy] || value;
+    if (value !== undefined) {
+        value = value[SelfProxy] || value;
+    }
     const curValue = target.__fields[prop];
     if (curValue === value || (curValue instanceof ProxyField && value instanceof RefField && curValue.fieldId === value[Id])) {
         // TODO This kind of checks correctly in the case that curValue is a ProxyField and value is a RefField, but technically
-- 
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