core/profile_select: Avoid uninitialized read in SelectProfile()

The default constructor of UUID doesn't initialize its data members, so
we need to directly initialize it to be invalid.

src/core/frontend/applets/profile_select.cpp

@@ -13,7 +13,8 @@ ProfileSelectApplet::~ProfileSelectApplet() = default;
 void DefaultProfileSelectApplet::SelectProfile(
     std::function<void(std::optional<Common::UUID>)> callback) const {
     Service::Account::ProfileManager manager;
-    callback(manager.GetUser(Settings::values.current_user.GetValue()).value_or(Common::UUID{}));
+    callback(manager.GetUser(Settings::values.current_user.GetValue())
+                 .value_or(Common::UUID{Common::INVALID_UUID}));
     LOG_INFO(Service_ACC, "called, selecting current user instead of prompting...");
 }