clear userId property of timeline by default in clearTimeline action

src/components/timeline/timeline.js

@@ -86,7 +86,7 @@ const Timeline = {
       if (this.newStatusCount === 0) return
 
       if (this.timeline.flushMarker !== 0) {
-        this.$store.commit('clearTimeline', { timeline: this.timelineName })
+        this.$store.commit('clearTimeline', { timeline: this.timelineName, excludeUserId: true })
         this.$store.commit('queueFlush', { timeline: this.timelineName, id: 0 })
         this.fetchOlderStatuses()
       } else {

src/modules/statuses.js

@@ -395,8 +395,9 @@ export const mutations = {
       state[key] = value
     })
   },
-  clearTimeline (state, { timeline }) {
-    state.timelines[timeline] = emptyTl(state.timelines[timeline].userId)
+  clearTimeline (state, { timeline, excludeUserId = false }) {
+    const userId = excludeUserId ? state.timelines[timeline].userId : undefined
+    state.timelines[timeline] = emptyTl(userId)
   },
   clearNotifications (state) {
     state.notifications = emptyNotifications()