From bdaef4a63179c418a26025294e9b2f59fdc06be5 Mon Sep 17 00:00:00 2001
From: psychedelicious <4822129+psychedelicious@users.noreply.github.com>
Date: Wed, 15 Nov 2023 06:33:34 +1100
Subject: [PATCH] fix: make `PanelOnResize` arg `prevMixedSizes` optional

It is `undefined` on first render.
---
 packages/react-resizable-panels/src/Panel.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/react-resizable-panels/src/Panel.ts b/packages/react-resizable-panels/src/Panel.ts
index e94d9d84f..e932580ef 100644
--- a/packages/react-resizable-panels/src/Panel.ts
+++ b/packages/react-resizable-panels/src/Panel.ts
@@ -19,7 +19,7 @@ export type PanelOnCollapse = () => void;
 export type PanelOnExpand = () => void;
 export type PanelOnResize = (
   mixedSizes: MixedSizes,
-  prevMixedSizes: MixedSizes
+  prevMixedSizes: MixedSizes | undefined
 ) => void;
 
 export type PanelCallbacks = {