Plugin: Function Plot

Hi @hieuthi , thanks for your reply!
I found the reason, it's the new Joplin version caused this error, as when I downgrade to Joplin v3.0.14, it works fine.

Joplin 3.0.14 (prod, darwin)

Client ID: eb2d1e1494234b77b3f9cd026a11b753
Sync Version: 3
Profile Version: 47
Keychain Supported: Yes

Revision: 05cf51e