Null Equals Null

A multi-tenant authorization check encoded as Python equality between two fields that can both legitimately be the unset sentinel (None, null, empty string). When both sides are unset, the equality returns true and the check waves the caller through. The sentinel that means "no tenant" becomes the membership of a shared default tenant, usually the largest population on the system. The fix is never raw equality, the comparison must explicitly assert that the value is non-null before allowing a match.