Does your underlying query or table have that filter applied? When an object is created, it inherits certain properties from the object it's based on, filter being one of them. So perhaps in the absence of a valid filter string it defaults to whatever is in the underlying data source. It's my habit to set filter on property to False as is recommended, not set it to an empty string and turn it on.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.