[BUG] category search in backend doesn't search correctly

[manuelgonzalez]

When i try to search a category in virtuemart backend it only find categories if there's categories in first level. Then it returns the correct search results. But if there's not a result in first category level, it returns no results.

Example: This is a category tree:

-Videogames
--Videogames
---PS3
---PSVita
---Wii
--Consoles

if i seach "games" it returns:

-Videogames
--Videogames

but if i search "Wii" it returns nothing.