Fix handling of bad update requests

We computed a safe area if a client gave us a bogus one, but we didn't
actually use it. Fix this properly and make sure we don't pass on bad
coordinates further.

common/rfb/VNCSConnectionST.cxx

@@ -874,7 +874,7 @@ void VNCSConnectionST::framebufferUpdateRequest(const Rect& r,bool incremental)
 
   // Just update the requested region.
   // Framebuffer update will be sent a bit later, see processMessages().
-  Region reqRgn(r);
+  Region reqRgn(safeRect);
   if (!incremental || !continuousUpdates)
     requested.assign_union(reqRgn);