qhttpthreaddelegate: check that we have a reply set when reading.

Make sure that we always have a reply set when we try to read.

Change-Id: Ib3ce9063bffc9810fc2a4fb52ee1a65b7f8cdfa0
Reviewed-by: Prasanth Ullattil <prasanth.ullattil@nokia.com>

src/network/access/qhttpthreaddelegate.cpp

@@ -374,6 +374,9 @@ void QHttpThreadDelegate::readBufferFreed(qint64 size)
 
 void QHttpThreadDelegate::readyReadSlot()
 {
+    if (!httpReply)
+        return;
+
     // Don't do in zerocopy case
     if (!downloadBuffer.isNull())
         return;