Serialize: Don't dereference unfilled pointers after a load fails

Containers of pointers are filled with nullptr and then DoClass'd, and
once an error switches the load to MODE_NOOP, every remaining element
called DoState on null.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

Common/Serialize/SerializeFuncs.h

@@ -66,6 +66,9 @@ void DoClass(PointerWrap &p, T *&x) {
 	if (p.mode == PointerWrap::MODE_READ) {
 		delete x;
 		x = new T();
+	} else if (p.mode == PointerWrap::MODE_NOOP && !x) {
+		// A load that failed partway leaves the rest of a container unfilled.
+		return;
 	}
 	x->DoState(p);
 }
@@ -76,6 +79,8 @@ void DoSubClass(PointerWrap &p, T *&x, Args... args) {
 		if (x != nullptr)
 			delete x;
 		x = new S(args...);
+	} else if (p.mode == PointerWrap::MODE_NOOP && !x) {
+		return;
 	}
 	x->DoState(p);
 }