From a0dcad3c0f5cced43a5af5834a4facef150ae410 Mon Sep 17 00:00:00 2001
From: VTHINKXIE <vthinkxie@users.noreply.github.com>
Date: Sat, 21 Oct 2017 01:45:37 -0500
Subject: [PATCH] fix(module:dropdown): fix unsubscribe undefined bug (#464)

close #269
---
 src/components/dropdown/nz-dropdown.component.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/components/dropdown/nz-dropdown.component.ts b/src/components/dropdown/nz-dropdown.component.ts
index 00d6f659af2..cddc519221d 100644
--- a/src/components/dropdown/nz-dropdown.component.ts
+++ b/src/components/dropdown/nz-dropdown.component.ts
@@ -154,7 +154,9 @@ export class NzDropDownComponent implements OnInit, OnDestroy, AfterViewInit {
   }
 
   ngOnDestroy() {
-    this._subscription.unsubscribe();
+    if (this._subscription) {
+      this._subscription.unsubscribe();
+    }
   }
 
   ngAfterViewInit() {