It says:"Response: After an opponent returns gold to the treasury during the taxation phase, add 1 gold from the treasury to Merchant's Widow."
Now I don't know that if my opponent has no gold in his gold pool when taxation begins, can I add 1 gold to Merchant's Widow.
I think I can do that. Because "returns gold to the treasury" is a game action, even if my opponent has no gold, he also has to
move
0 gold token to the treasury.
Am I right?