xP/xW: fix buffer rename handling

Maintaining string pointers to the current/last buffer
means that renames invalidate them.

xP/public/xP.js

@@ -344,6 +344,11 @@ rpcEventHandlers.set(Relay.Event.BufferStats, e => {
 rpcEventHandlers.set(Relay.Event.BufferRename, e => {
 	buffers.set(e.new, buffers.get(e.bufferName))
 	buffers.delete(e.bufferName)
+
+	if (e.bufferName === bufferCurrent)
+		bufferCurrent = e.new
+	if (e.bufferName === bufferLast)
+		bufferLast = e.new
 })
 
 rpcEventHandlers.set(Relay.Event.BufferRemove, e => {