[Filter Text Box] It is not possible to delete a previously applied filter

[mastropi]

When we write a filter the first time, everything works fine.
However we cannot delete the filter later on, because the application searches for previously applied filters and the DEL or BACKSPACE operator do not work --they actually work initially, but when we delete the whole text, the previously applied filter is suddenly shown again)

The picture below tries to convey this issue --where we see the previously written filter listed below the filter text box as a possible selection for the user.