The bug occur when I am editing Chinese Wikipedia using VisualEditor. When I try to add link or citation to my page it always redirect me to the page https://zh.wikipedia.org/w/undefined which makes me unable to edit anythings. How can this problem be solved? Thank you.
P.S. I have tried serval times on other Languages' Wikipedia (e.g. English and Japanese) and no problem show up. Seems this bug only occur in Chinese Wikipedia.
P.S.2 The problem only occur on desktop version but not mobile version.