.toValuesOf returning empty set when one of extracted values is null

[szczursonn]

SOQL's .toValuesOf(field) method returns an empty Set when one of the queried records has the field as null

STEPS TO REPRODUCE

1. Create two Account records: one where Industry field is null, and one where Industry field is populated
2. Run a query with .toValuesOf:

System.debug(SOQL.of(Account.sObjectType).toValuesOf(Account.Industry));
// {}

4. Run the same query, but filter out null values from the field:

System.debug(SOQL.of(Account.sObjectType).whereAre(SOQL.Filter.with(Account.Industry).isNotNull()).toValuesOf(Account.Industry));
// {Education, Mining, Manufacturing...}

Expected behavior

.toValuesOf(field) returns a Set with all values when extracting a nullable field, including null