Bug 1396307 - Add null check in nsHttpChannel::OnAuthAvailable r=michal

MozReview-Commit-ID: L9zaroxJ72i

--HG--
extra : rebase_source : 4ae01e3889b5e1cd3708e9a1273b7e0eb79aca51

netwerk/protocol/http/nsHttpChannel.cpp

@@ -5863,7 +5863,9 @@ NS_IMETHODIMP nsHttpChannel::OnAuthAvailable()
     mAuthRetryPending = true;
     mProxyAuthPending = false;
     LOG(("Resuming the transaction, we got credentials from user"));
-    mTransactionPump->Resume();
+    if (mTransactionPump) {
+        mTransactionPump->Resume();
+    }
 
     return NS_OK;
 }