webterm: avoid needless %blew tasks

Any change to the session object was triggering this. But that now includes
an "unacked keystrokes" counter, which updates frequently, and we
definitely don't want to send resize notifications in that case.

pkg/interface/webterm/Buffer.tsx

@@ -271,7 +271,7 @@ export default function Buffer({ name, selected, dark }: BufferProps) {
       await api.poke(pokeTask(name, { blew: { w: session.term.cols, h: session.term.rows } }));
       session.term.focus();
     }
-  }, [session, selected]);
+  }, [session?.term, selected]);
 
   // Effects
   // init session