[frontend] fix nightly update checker again (#3446)

I ❤️ std::optional

Signed-off-by: crueter <[email protected]>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3446

src/frontend_common/update_checker.cpp

@@ -176,6 +176,5 @@ std::optional<UpdateChecker::Update> UpdateChecker::GetUpdate() {
     }
 
 empty:
-    return UpdateChecker::Update{};
-
+    return std::nullopt;
 }