Network/NetPacket: Allow empty pointer for NetPacket creating (won't initialize memory)

include/Nazara/Network/NetPacket.inl

@@ -155,6 +155,8 @@ namespace Nz
 	{
 		InitStream(HeaderSize + size, HeaderSize, OpenMode_ReadOnly);
 		m_buffer->Resize(HeaderSize + size);
+
+		if (ptr)
 			std::memcpy(m_buffer->GetBuffer() + HeaderSize, ptr, size);
 
 		m_netCode = netCode;