Userland: Make IPC handlers return void if they don't have any outputs

Author: https://github.com/gunnarbeutner
Commit: 889359b6f9
Pull-request: https://github.com/SerenityOS/serenity/pull/6805
Reviewed-by: https://github.com/alimpfard

Userland/Services/ImageDecoder/ClientConnection.cpp

@@ -30,9 +30,8 @@ void ClientConnection::die()
     exit(0);
 }
 
-Messages::ImageDecoderServer::GreetResponse ClientConnection::handle(const Messages::ImageDecoderServer::Greet&)
+void ClientConnection::handle(const Messages::ImageDecoderServer::Greet&)
 {
-    return {};
 }
 
 Messages::ImageDecoderServer::DecodeImageResponse ClientConnection::handle(const Messages::ImageDecoderServer::DecodeImage& message)