vm_ptr: return nullptr and add some nullptr deref checks

rpcs3/Emu/Memory/vm_ptr.h

@@ -101,23 +101,39 @@ namespace vm
 			return vm::cast(m_addr);
 		}
 
+		template <bool Strict = false>
 		T* get_ptr() const
 		{
-			return static_cast<T*>(vm::base(vm::cast(m_addr)));
+			if (operator bool()) [[likely]]
+			{
+				return static_cast<T*>(vm::base(vm::cast(m_addr)));
+			}
+
+			if constexpr (Strict)
+			{
+				fmt::throw_exception("Invalid pointer");
+			}
+
+			return nullptr;
 		}
 
 		T* operator ->() const requires (!std::is_void_v<T>)
 		{
-			return get_ptr();
+			return get_ptr<true>();
 		}
 
 		std::add_lvalue_reference_t<T> operator *() const requires (!std::is_void_v<T>)
 		{
-			return *static_cast<T*>(vm::base(vm::cast(m_addr)));
+			return *get_ptr<true>();
 		}
 
 		std::add_lvalue_reference_t<T> operator [](u32 index) const requires (!std::is_void_v<T>)
 		{
+			if (operator bool() == false) [[unlikely]]
+			{
+				fmt::throw_exception("Invalid pointer");
+			}
+
 			return *static_cast<T*>(vm::base(vm::cast(m_addr) + u32{sizeof(T)} * index));
 		}