fix: don't give shared pointer to obj. external to the model

It causes some weird problems and adds refcounting overhead.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/minecraft/mod/Mod.h

@@ -47,6 +47,7 @@ class Mod : public Resource
     Q_OBJECT
 public:
     using Ptr = shared_qobject_ptr<Mod>;
+    using WeakPtr = QPointer<Mod>;
 
     Mod() = default;
     Mod(const QFileInfo &file);