I'd be wary of using it again. Most of the nutrients will have been exhaused because tomatoes are heavy feeders. Also, last year was a very bad year for tomato blight and even if your tomatoes cropped well, some blight spores may have got into the compost which could infect this year's plants. Even adding liquid feed may not be sufficient. However, rather than waste the bag, you could try growing something different in it, such as salad leaves or possible even one or two strawberry plants.