Safeguard against nil or empty target

[theJenix]

Added code to safeguard against a nil or empty target string. In the case of a nil or empty target string, both commands are inhibited.

[ram-nadella]

Good catch. I see your approach and I think we can do this with fewer changes, here is how I see it, let me know what you think:

CGI.escape works fine with empty strings, it's nil that causes the error. So how about adding a line like the following in target_text() before we do the escaping

return "" if selection.nil? && current_word.nil?

Also I would prefer to skip the check before executing the command because that way the user can still launch Dash with the same commands and do a search if they want to