Add an input check for datastore option PORTS

If Rex::Socket.portspec_crack returns an empty array, we assume
there are no valid ports to test, so we raise an OptionValidateError
to warn the user about it.

Author: wchen-r7

modules/auxiliary/scanner/misc/poisonivy_control_scanner.rb

@@ -41,6 +41,10 @@ def run_host(ip)
 
     ports = Rex::Socket.portspec_crack(datastore['PORTS'])
 
+    if ports.empty?
+      raise Msf::OptionValidateError.new(['PORTS'])
+    end
+
     while(ports.length > 0)
       t = []
       r = []