Fix invalid null comparison in RideList sort comparator

The previous comparator returned false when either rideLhs or rideRhs was a nullptr, in an attempt to avoid null pointer dereference. However, this causes both comp(a, nullptr) and comp(nullptr, a) to return false, which violates the requirements of a strict weak ordering.

As defined in the C++ standard, the comparator used in std::sort must establish a strict weak ordering. This includes the requirement that the equivalence relation defined as
equiv(a, b) := !comp(a, b) && !comp(b, a) must be transitive.

In the original logic, two non-null elements a and b might be ordered such that comp(a, b) == true but if both comp(a, nullptr) and comp(b, nullptr) return false, then equiv(a, nullptr) == true and equiv(b, nullptr) == true, which implies equiv(a, b) == true. This contradicts comp(a, b) == true and violates transitivity of equiv.

Such violations can lead to undefined behavior in std::sort, including invalid memory access or segmentation faults.

Fix the comparator to consistently treat nullptr as greater than any non-null pointer, by returning rideLhs != nullptr when either pointer is null. This restores transitivity and compliance with the C++ standard, ensuring reliable and predictable sorting behavior.

src/openrct2-ui/windows/RideList.cpp

@@ -818,7 +818,7 @@ namespace OpenRCT2::Ui::Windows
                 const Ride* rideRhs = GetRide(rhs.Id);
                 if (rideLhs == nullptr || rideRhs == nullptr)
                 {
-                    return false;
+                    return rideLhs != nullptr;
                 }
                 return !pred(*rideLhs, *rideRhs);
             });