Check signal_id is set before using it
Check signal_id is set before using it

Change-Id: I421afb858ee33e17de3c12c8af7103e3ac9e422d
Reviewed-on: http://gerrit.aldebaran.lan/53934
Reviewed-by: pdaouadi <fc1eb3334d3fdad315bae23aa166bc70bd434067@aldebaran-robotics.com>
Tested-by: ncornu <13ba26b8f12d26c819f48749c65f2f7f5c1d13db@aldebaran-robotics.com>

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