Fix bug.

lib/tasks/exec_command.rake

@@ -219,6 +219,7 @@ namespace :exec_commands do
                   end
                 end
                 new_arr = output_lines[1..-1]
+                new_arr = [] if new_arr.nil?
                 if data_str[-1] == "\n"
                   new_arr << ""
                 end