Improve handling of deleted posts

src/view/com/notifications/FeedItem.tsx

@@ -43,6 +43,11 @@ export const FeedItem = observer(function FeedItem({
     }
   }, [item])
 
+  if (item.additionalPost?.notFound) {
+    // don't render anything if the target post was deleted or unfindable
+    return <View />
+  }
+
   if (item.isReply) {
     return (
       <Link href={itemHref} title={itemTitle}>

src/view/com/post-thread/PostThreadItem.tsx

@@ -88,6 +88,15 @@ export const PostThreadItem = observer(function PostThreadItem({
     )
   }
 
+  if (deleted) {
+    return (
+      <View style={[styles.outer, s.p20, s.flexRow]}>
+        <FontAwesomeIcon icon={['far', 'trash-can']} style={[s.gray4]} />
+        <Text style={[s.gray5, s.ml10]}>This post has been deleted.</Text>
+      </View>
+    )
+  }
+
   if (item._isHighlightedPost) {
     return (
       <>

src/view/shell/mobile/index.tsx

@@ -321,7 +321,7 @@ export const MobileShell: React.FC = observer(() => {
         <Btn
           icon={isAtHome ? 'home-solid' : 'home'}
           onPress={onPressHome}
-          onLongPress={doNewTab('/')}
+          onLongPress={TABS_ENABLED ? doNewTab('/') : undefined}
         />
         {TABS_ENABLED ? (
           <Btn
@@ -333,7 +333,7 @@ export const MobileShell: React.FC = observer(() => {
         <Btn
           icon={isAtNotifications ? 'bell-solid' : 'bell'}
           onPress={onPressNotifications}
-          onLongPress={doNewTab('/notifications')}
+          onLongPress={TABS_ENABLED ? doNewTab('/notifications') : undefined}
           notificationCount={store.me.notificationCount}
         />
         <Btn