This fixes two closely-related bugs:
1. When loading tasks from a bucket of a saved filter, the saved filter query would override the user-supplied filter, which would cause to only tasks matching the saved filter query to be returned.
2. When a filter query for a bucket was specified, the function would only check if one of the top level filters was a filter for tasks in a specific bucket. That means a filter like "bucket_id = 42 && labels = foo" would return the expected result, while a filter like "labels = foo && (bucket_id = 42 && priority = 1)" would fail with an error 500 because the task_buckets table was not joined to the sql query. The fix from the first bug caused such filter queries.
425f6378c6