keybindings: fix error on alt+h

Fixes the following JS error:

    TypeError: e.setReceipt is not a function

state.js

@@ -85,6 +85,16 @@ export function getServerName(server, bouncerNetwork) {
 	}
 }
 
+export function receiptFromMessage(msg) {
+	// At this point all messages are supposed to have a time tag.
+	// App.addMessage ensures this is the case even if the server doesn't
+	// support server-time.
+	if (!msg.tags.time) {
+		throw new Error("Missing time message tag");
+	}
+	return { time: msg.tags.time };
+}
+
 export function isMessageBeforeReceipt(msg, receipt) {
 	if (!receipt) {
 		return false;