Can I safely thaw and refreeze sorbet?
Sorbet are typically acidic(from the fruit juices) and contain sugar. Both of these act as preservatives in addition to the extremely cold temperatures that sorbets are kept at. So it is perfectly okay to melt your sorbet ice block. However when you melt the sorbet block, you will want to do it slowly. Fruit/herb flavors are very volatile so if the mixture is over heated, the flavoring will break down and the taste will deteriorate. 

When refreezing your mixture, you might want to consider adding a little more sugar into the mixture to prevent it from freezing so hard in the future. Sorbet sugar by concentration is usually around 20-30%. If your sorbet is sweet enough, then you may also add a little tasteless alcohol like vodka to prevent the sorbet from freezing too hard.