I faced the problem on one of my VPS that leaded to the situation when the system kills ClamAv daemon that allocated all the memory during update. The server has only 4Gb of RAM and I didn't want to increase it as this will increase the payment for this server. Keeping in mind that except of this problem with ClamAv everything works fine I decided to fix this by adding the swap so the system can use it during ClamAv update.