[ASTERIXDB-2289][COMP] Fix field access with CASE - user model changes: no - storage format changes: no - interface changes: no
Details: This patch fixes field access in the presense CASE and JOIN. This is a scenario where push-down-field-access rule throws an exception if the field access has potentially two sources and it could not push down the field access to left or right branch. Don't throw an exception and just return false (i.e. field access was not pushed) instead of throwing an exception.