Keep the filter for the first esc-press

Only clear the sub query when pressing esc in the search box. Clear everything if no subquery is present.

Example:

`[  andr|setType  ]`, **ESC**, `[  andr|  ]`, **ESC**, `[  ]`

`[  simplequery  ]`, **ESC**, `[  ]`

p.s. sorry for the flood of PRs. I'm just scratching my own itches here, let me know if I should keep the changes to myself ;)