narrow: Remove blueslip error code line.

When clicking on a message from an archived
stream, the `adjusted_terms` may be null since
archived streams are not sent back to the client.
This results in an error for the user.

web/src/message_view.ts

@@ -502,7 +502,6 @@ export function show(raw_terms: NarrowTerm[], show_opts: ShowMessageViewOpts): v
                     );
 
                     if (adjusted_terms === null) {
-                        blueslip.error("adjusted_terms impossibly null");
                         return;
                     }