ctrl "wander" segfaults after warning "Model r0.ranger:1 not found" about stage

[sloretz]

A workaround is to add a second ranger sensor to the robot. The crash happens because the wander controller tries to subscribe to two rangers.

define amigobot position
(
  size [0.330 0.280 0.25]
  origin [0 0 0 0] # what should this value be? send email to [email protected].
  amigo_sonar ( pose [0 0 -0.02 0 ] )
  amigo_sonar( pose [0 0 -0.02 1 ] )    # Added this line
)

I think it would be useful for the wander controller to write to std_err about needing two rangers when it's asked to control a robot without them.

[rtv]

Fixed in master.