Bug: ELSE gets removed from CASE statement inside function

[quassy]

What Happened

ELSE option is removed from CASE statement

CREATE OR REPLACE FUNCTION get_grade(
    percentage FLOAT64
)
RETURNS STRING
AS (
    CASE
        WHEN percentage > 80 THEN 'A'
        WHEN percentage > 40 THEN 'B'
    END
);

Expected Behaviour

ELSE option should be kept

CREATE OR REPLACE FUNCTION get_grade(
    percentage FLOAT64
)
RETURNS STRING
AS (
    CASE
        WHEN percentage > 80 THEN 'A'
        WHEN percentage > 40 THEN 'B'
        ELSE 'C'
    END
);

How to reproduce

CREATE OR REPLACE FUNCTION get_grade(
    percentage FLOAT64
)
RETURNS STRING 
AS (
    CASE
        WHEN percentage > 80 THEN 'A'
        WHEN percentage > 40 THEN 'B'
        ELSE 'C'
    END
);

Configuration

[sqruff]
dialect = bigquery
rules = all

---

At least in playground I could not even get a simple SELECT CASE to return anything:

    select CASE
        WHEN percentage > 80 THEN 'A'
        WHEN percentage > 40 THEN 'B'
        ELSE 'C'
    END as grade
    from table;