Token Abilities Not Fully Whispering?

I'm having some issues getting my monsters to whisper their entire attack rolls. For example, when a goblin token uses the following ability (/w gm %{selected|repeating_npcaction_$0_npc_action}), the meat of the roll is properly whispered, but a blank message is sent to the all chat, betraying the stealth of the roll. This is illustrated in the attached screenshot. Does anyone know what's causing this, and how to fix or work around it?

Is this a macro that you are using to call the ability? If so, I would check to see if there is an empty line at the end of the macro.

... oh my god I can't believe that was the problem Thanks so much for pointing out my undetectable idiocy!

Comes from experience. Don't worry, we have all done that before, it's how we know what was wrong. Happy rolling!