Address rqt_reconfigure crashing with IndexError

[rolaechea]

This fixes rqt_reconfigure crashing with an index error as reported in bug #92 .

In certain cases, the list of nodes names include an empty string as the name of a node (mostly when a node has crashed or segfaulted) -- looking it up resulted in the index error reported in bug #92 and rqt reconfigure crashing. The solution is just to skip that "node".

[rolaechea]

I agree that a workaround for now is a good idea.

@mjeronimo I don't know the exact root cause, but I do know that the proximate cause is that dynamic_reconfigure.find_reconfigure_services returns an element that is "" when a ros node has not exited properly . And that find_reconfigure_services executes the following code :

def find_reconfigure_services():
import rosservice
return sorted([s[:-len('/set_parameters')] for s in rosservice.get_service_list() if s.endswith('/set_parameters')])