I am not Monkey
Thinking of it, perhaps I started from wrong direction.
The action should not happen at first place if there's nothing coded. That means if that action takes place, it was coded. Now all you need is to find the code and remove it.
What's in yours on_mouse_click function?
Do you maybe have some "Look at inventory" event handlers for your inventory items?
Also: is your game based on any game template?