Fix session removal code, prevent missing transport param fail

lib/rex/post/meterpreter/client_core.rb

@@ -558,7 +558,11 @@ class ClientCore < Extension
   # Indicates if the given transport is a valid transport option.
   #
   def valid_transport?(transport)
-    VALID_TRANSPORTS.has_key?(transport.downcase)
+    if transport
+      VALID_TRANSPORTS.has_key?(transport.downcase)
+    else
+      false
+    end
   end
 
   private

lib/rex/post/meterpreter/packet_dispatcher.rb

@@ -79,7 +79,9 @@ module PacketDispatcher
 
   def shutdown_passive_dispatcher
     return if not self.passive_service
-    self.passive_service.remove_resource(self.conn_id  + "/")
+    resource = self.conn_id
+    resource += "/" unless resource.end_with?("/")
+    self.passive_service.remove_resource(resource)
 
     # If there are no more resources registered on the service, stop it entirely
     if self.passive_service.resources.empty?

lib/rex/post/meterpreter/ui/console/command_dispatcher/core.rb

@@ -281,10 +281,6 @@ class Console::CommandDispatcher::Core
   # Disconnects the session
   #
   def cmd_detach(*args)
-    if not client.passive_service
-      print_error("Detach is only possible for non-stream sessions (http/https)")
-      return
-    end
     client.shutdown_passive_dispatcher
     shell.stop
   end