You can’t do it within the Chest.
If you restore it to original place (or move to another folder) avast could repair it. The Standard Shield will detect it again and then you can choose the repair option. Avast would be able to do it if the file is a repairable executable file (handled by avast: not all executable could be repaired) and better if the informations of original one is stored into the VRDB (see ‘FAQ’ on my signature for more info about VRDB) 