From 54e832d080a5699d13e37760c7a00309629e899c Mon Sep 17 00:00:00 2001
From: chunghha <chunghha@users.noreply.github.com>
Date: Wed, 19 May 2021 09:59:04 -0500
Subject: [PATCH] fix(material/sort): fix undefined object access (#22634)

(cherry picked from commit 68600b8f4301bd56e6411f2ac1ba5637691ed650)
---
 src/material/sort/sort-header.ts          | 6 +++---
 tools/public_api_guard/material/sort.d.ts | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/material/sort/sort-header.ts b/src/material/sort/sort-header.ts
index f42c9392eecb..0e6fb5378e6a 100644
--- a/src/material/sort/sort-header.ts
+++ b/src/material/sort/sort-header.ts
@@ -54,7 +54,7 @@ export type ArrowViewState = SortDirection | 'hint' | 'active';
  */
 export interface ArrowViewStateTransition {
   fromState?: ArrowViewState;
-  toState: ArrowViewState;
+  toState?: ArrowViewState;
 }
 
 /** Column definition associated with a `MatSortHeader`. */
@@ -112,7 +112,7 @@ export class MatSortHeader extends _MatSortHeaderMixinBase
    * position through the animation. If animations are currently disabled, the fromState is removed
    * so that there is no animation displayed.
    */
-  _viewState: ArrowViewStateTransition;
+  _viewState: ArrowViewStateTransition = { };
 
   /** The direction the arrow should be facing according to the current state. */
   _arrowDirection: SortDirection = '';
@@ -224,7 +224,7 @@ export class MatSortHeader extends _MatSortHeaderMixinBase
    * no animation appears.
    */
   _setAnimationTransitionState(viewState: ArrowViewStateTransition) {
-    this._viewState = viewState;
+    this._viewState = viewState || { };
 
     // If the animation for arrow position state (opacity/translation) should be disabled,
     // remove the fromState so that it jumps right to the toState.
diff --git a/tools/public_api_guard/material/sort.d.ts b/tools/public_api_guard/material/sort.d.ts
index 8b882b5396d5..93ecabbecd32 100644
--- a/tools/public_api_guard/material/sort.d.ts
+++ b/tools/public_api_guard/material/sort.d.ts
@@ -2,7 +2,7 @@ export declare type ArrowViewState = SortDirection | 'hint' | 'active';
 
 export interface ArrowViewStateTransition {
     fromState?: ArrowViewState;
-    toState: ArrowViewState;
+    toState?: ArrowViewState;
 }
 
 export declare const MAT_SORT_DEFAULT_OPTIONS: InjectionToken<MatSortDefaultOptions>;