Always best to take the action that is least likely to do harm, if it turns out to be a false positive (probably not the case here), FP. avast! usually only shows the actions that can be attempted (not greyed out).

Repair, should be your first choice (not always possible, trojans, generally can’t be repaired).
Move to Chest, here nothing in the file can do any harm, you can check it out (ask here if need be), you can restore it to its original location (if FP), if after a period with no adverse effect, you can delete it from the chest.
Delete - I would not advise this as a first course of action unless you are really certain - Act in haste Repent at leisure.

All may not be lost, you don’t need to boot into safe mode, just be able to boot for the time being. Have you tried that, if it boots schedule a boot-time scan from with in avast!

Also have you looked at the information in the link I gave you (The link is the blue text)?