added comments

src/page/subscriptions/index.js

@@ -1,5 +1,6 @@
 import { connect } from 'react-redux';
 import {
+  doChannelUnsubscribe,
   doFetchMySubscriptions,
   doSetViewMode,
   doFetchRecommendedSubscriptions,
@@ -36,6 +37,7 @@ const select = state => ({
 });
 
 const perform = dispatch => ({
+  channelUnsubscribe: subscription => dispatch(doChannelUnsubscribe(subscription)),
   doFetchMySubscriptions: () => dispatch(doFetchMySubscriptions()),
   doFetchRecommendedSubscriptions: () => dispatch(doFetchRecommendedSubscriptions()),
   doSetViewMode: viewMode => dispatch(doSetViewMode(viewMode)),

src/page/subscriptions/view.js

@@ -82,6 +82,8 @@ class SubscriptionsPage extends React.PureComponent {
     if (Constants.DRAWER_ROUTE_SUBSCRIPTIONS === currentRoute && currentRoute !== prevRoute) {
       this.onComponentFocused();
     }
+
+    this.unsubscribeShortChannelUrls();
   }
 
   handleSortByItemSelected = item => {
@@ -109,6 +111,16 @@ class SubscriptionsPage extends React.PureComponent {
     return [Constants.ALL_PLACEHOLDER].concat(channelUris);
   };
 
+  // Added in 0.12.1. Can be dropped on or after 1 Feb 2020.
+  unsubscribeShortChannelUrls = () => {
+    // this should only have to happen once
+    const { subscribedChannels, channelUnsubscribe } = this.props;
+    const badSubs = subscribedChannels.filter(sub => sub.uri.split('#')[1].length < 5);
+    if (badSubs.length > 0) {
+      badSubs.forEach(sub => channelUnsubscribe(sub));
+    }
+  };
+
   render() {
     const {
       suggestedChannels,