ssb: Fix an instance of channels being stuck unread.

apps/ssb/tf-tab-news-feed.js

@@ -13,6 +13,7 @@ class TfTabNewsFeedElement extends LitElement {
 			drafts: {type: Object},
 			expanded: {type: Object},
 			channels_unread: {type: Object},
+			channels_latest: {type: Object},
 			loading: {type: Number},
 			time_range: {type: Array},
 			time_loading: {type: Array},
@@ -31,6 +32,7 @@ class TfTabNewsFeedElement extends LitElement {
 		this.drafts = {};
 		this.expanded = {};
 		this.channels_unread = {};
+		this.channels_latest = {};
 		this.start_time = new Date().valueOf();
 		this.time_range = [0, 0];
 		this.time_loading = undefined;
@@ -320,7 +322,7 @@ class TfTabNewsFeedElement extends LitElement {
 	mark_all_read() {
 		let newest = this.messages.reduce(
 			(accumulator, current) => Math.max(accumulator, current.rowid),
-			-1
+			this.channels_latest[this.channel()] ?? -1
 		);
 		if (newest >= 0) {
 			this.dispatchEvent(