fix: add a return statement after setting the response

Author: asimm241

src/api/routes/rosetta/construction.ts

@@ -198,6 +198,7 @@ export function createRosettaConstructionRouter(db: DataStore): RouterWithAsync
         }
       } catch (e) {
         res.status(400).json(RosettaErrors.invalidPublicKey);
+        return;
       }
     }