I can't find a contact for the author. There doesn't seem to be a way to report an issue on the node's project page https://flows.nodered.org/node/node-red-contrib-totaliser
I've sent him a message on this forum and hope he might see that.
In the meantime I've edited totaliser.js on my system and confirm that setting msg.payload to 'reset' no longer causes a ReferenceError.
node.startTime = Date.now();