Fix NPE if stopping navigation in onBeforeUnload (#19541)

Change-Id: Idcba5ceeff9df88a4ea7fe6b34e2e2537b7ee58c

1 files changed, 8 insertions, 0 deletions

diff --git a/client/src/com/vaadin/client/communication/XhrConnection.java b/client/src/com/vaadin/client/communication/XhrConnection.java
index ff8155259e..11e3cf3cb7 100644
--- a/client/src/com/vaadin/client/communication/XhrConnection.java
+++ b/client/src/com/vaadin/client/communication/XhrConnection.java
@@ -254,6 +254,14 @@ public class XhrConnection {
     private static native boolean resendRequest(Request request)
     /*-{
         var xhr = request.@com.google.gwt.http.client.Request::xmlHttpRequest
+        if (xhr == null) {
+            // This might be called even though the request has completed,
+            // if the webkitMaybeIgnoringRequests has been set to true on beforeunload
+            // but unload was cancelled after that. It will then stay on until the following
+            // request and if that request completes before we get here (<250mS), we will
+            // hit this case.
+            return false;
+        }
         if (xhr.readyState != 1) {
             // Progressed to some other readyState -> no longer blocked
             return false;