Fixed bug: must remove old mapping when changing channel name

src/content_working_group/lib.rs

@@ -2383,6 +2383,13 @@ impl<T: Trait> Module<T> {
     ) {
         // Update name to channel mapping if there is a new name mapping
         if let Some(ref channel_name) = new_channel_name {
+
+            // Remove mapping under old name
+            let current_channel_name = ChannelById::<T>::get(channel_id).channel_name;
+
+            ChannelIdByName::<T>::remove(current_channel_name);
+
+            // Establish mapping under new name
             ChannelIdByName::<T>::insert(channel_name.clone(), channel_id);
         }