Reference for Avodah Zarah 105:1

דרבי וולס לא נצרכה שיש לו בה שותפות וקמ"ל ישראל הוא דלא מבטל דעובד כוכבים אבל עובד כוכבים דנפשיה מבטל

R. Volas said: No, the clause is necessary for the circumstance where there was joint-ownership; and it teaches us that while the Israelite cannot annul [the part of] the idol which belongs to the non-Jew, the idolater can annul [the part] which belongs to himself.

Jastrow