kernel/thread: Fix potential crashes introduced in 26de4bb521

This amends cases where crashes can occur that were missed due to the
odd way the previous code was set up (using 3DS memory regions that
don't exist).

src/core/hle/kernel/thread.h

@@ -265,6 +265,8 @@ public:
 private:
     Thread();
     ~Thread() override;
+
+    std::shared_ptr<std::vector<u8>> tls_memory = std::make_shared<std::vector<u8>>();
 };
 
 /**