What is the ruling on attending a dinner invitation at a friend's house without knowing it is a birthday celebration for a family member, with suspicion arising due to the invitation date coinciding with the birthday and the serving of cake after dinner?

"It is not legislated to celebrate the birth of anyone, because it is an innovation (bid'ah) if done as an act of worship, and an innovated feast if done as a custom. Furthermore, it involves imitating non-Muslims. If one is invited to a banquet and knows or strongly suspects that it is a celebration of a birthday, it is not permissible for him to attend, because it entails condoning evil and assisting in it. Allah says: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression)."