I'd say that if you did not experience fungal infection of your tomatoes last year you should be safe to go this year. If you're still concerned, however, at the very least you could find a product called Dormant Oil. This product is a Horticultural oil, which is normally used for control of insects. However, if you mix 1 tabelspoon of the oil and one tablespoon of standard Baking Soda with the required gallon of water, it will control any and all fungi. It's simply sprayed on any soil before planting. I use it extensively to overcome Black Spot on Roses which is a fungus related to the various 'wilt' fungi on tomatoes...
Dig in some organic matter, like home made compost or well rotted manure. Grow a different crop this year, and all will be fine. Why not try peppers, french beans, aubergenes, or cucumber, all will do well in the greenhouse. Good Luck
I have used the same soil successfully for growing tomatoes for more than one year. After a few years I try to sterilize the soil though am not sure that there are any suitable products that are now legal to use. The alternative is to dig largish holes and fill with fresh compost and then plant the tomatoes leaving the remaining soil around the holes.
also plant french marigolds inbetween your tomato plants - helps with pest control- white fly hate the smell of them and the roots spread in the soil and kill nematodes. Don't plant near beans though. happy gardening