fix(fastify): return the response on exception

Fastify requires us to return the response object when handling async
methods and dealing with exceptions, otherwise a thenable gets wrapped
and improperly handled later causing an exception. This is shown by
[this repo][1] and discuessed in [this issue][2].

[1]: https://github.com/sgrigorev/nestjs-compress-issue
[2]: fastify/fastify-compress#215 (comment)

packages/core/router/router-proxy.ts

@@ -22,6 +22,7 @@ export class RouterProxy {
       } catch (e) {
         const host = new ExecutionContextHost([req, res, next]);
         exceptionsHandler.next(e, host);
+        return res;
       }
     };
   }
@@ -46,6 +47,7 @@ export class RouterProxy {
       } catch (e) {
         const host = new ExecutionContextHost([req, res, next]);
         exceptionsHandler.next(e, host);
+        return res;
       }
     };
   }