make sure we can actually invoke auto targeting before adding it

Author: busterb

lib/msf/core/exploit.rb

@@ -294,7 +294,7 @@ def initialize(info = {})
         # Don't add the automatic target unless there's already more than one target to pick from
         if info['Targets'].count > 1
           # Finally, only add the target if there is a remote host option
-          if self.options['RHOST']
+          if self.respond_to?(:rhost) && self.respond_to?(:auto_targeted_index)
             auto = ["Automatic", { 'AutoGenerated' => true}]
             info['Targets'].unshift(auto)
           end