Remove window from observers when it's closed instead of deleted.

atom/browser/api/atom_api_window.cc

@@ -75,8 +75,6 @@ Window::Window(base::DictionaryValue* options)
 
 Window::~Window() {
   Emit("destroyed");
-
-  window_->RemoveObserver(this);
 }
 
 void Window::OnPageTitleUpdated(bool* prevent_default,
@@ -99,9 +97,13 @@ void Window::WillCloseWindow(bool* prevent_default) {
 void Window::OnWindowClosed() {
   Emit("closed");
 
-  // Free memory when native window is closed, the delete is delayed so other
-  // observers would not get a invalid pointer of NativeWindow.
-  base::MessageLoop::current()->DeleteSoon(FROM_HERE, window_.release());
+  if (window_) {
+    window_->RemoveObserver(this);
+
+    // Free memory when native window is closed, the delete is delayed so other
+    // observers would not get a invalid pointer of NativeWindow.
+    base::MessageLoop::current()->DeleteSoon(FROM_HERE, window_.release());
+  }
 }
 
 void Window::OnWindowBlur() {