Can't uninstall UDF if the implementation library file doesn't exist

When an installed UDF can't be loaded at startup as its .so file can't be found anymore,, the error log will contain warnings about not being able to load the function

[ERROR] Can't open shared library 'udf_test.so' (errno: 0, cannot open shared object file: No such file or directory)

but the function can't be removed with DROP FUNCTION:

MariaDB [(none)]> drop function foo;

ERROR 1305 (42000): FUNCTION (UDF) foo does not exist

It can only be removed by deleting the related row in the mysql.func table directly with

DELETE FROM mysql.func WHERE name='...'

It should be able to remove a function with DROP even if it couldn't initialize for whatever reason, including missing .so file