Speculative fix for crash happening on opening network settings

Adding null check for system tray client and deleting bubble
after all other code has executed.

Bug: 1163636
Change-Id: I6522dcf42a4909dffc8e1cfa8c6a56112d4c7319
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615673Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841267}

ash/system/network/network_state_list_detailed_view.cc

@@ -323,10 +323,17 @@ void NetworkStateListDetailedView::ShowSettings() {
   Shell::Get()->metrics()->RecordUserMetricsAction(
       list_type_ == LIST_TYPE_VPN ? UMA_STATUS_AREA_VPN_SETTINGS_OPENED
                                   : UMA_STATUS_AREA_NETWORK_SETTINGS_OPENED);
+
+  SystemTrayClient* system_tray_client =
+      Shell::Get()->system_tray_model()->client();
+
+  if (system_tray_client) {
+    system_tray_client->ShowNetworkSettings(
+        model_->default_network() ? model_->default_network()->guid
+                                  : std::string());
+  }
+
   CloseBubble();  // Deletes |this|.
-  Shell::Get()->system_tray_model()->client()->ShowNetworkSettings(
-      model_->default_network() ? model_->default_network()->guid
-                                : std::string());
 }
 
 void NetworkStateListDetailedView::UpdateHeaderButtons() {