handleFuture: Fix handling of Future<void>.
handleFuture: Fix handling of Future<void>.

Change-Id: I90a9682f9aeff04d4def979239a4d73d39e47214
Reviewed-on: http://gerrit.aldebaran.lan/34419
Reviewed-by: cgestes <ddb78fe00abb42f91254c16a0860e38eb0781789@aldebaran-robotics.com>
Reviewed-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>
Tested-by: mnottale <e3ccf1b6558404e921a21fa09cebb1153b50ec36@aldebaran-robotics.com>

aldebaran/libqi,aldebaran/libqi,bsautron/libqi,vbarbaresi/libqi,aldebaran/libqi