Show Chat Update time if last message time doesn't exist

[AmineMekki01]

Some chats are created but the user didn't send a message. So we can't show the last message time in the chats. There 2 things for this :

• Wither we delete the chats after a certain period since no message was sent
• We just show when the chat was updated instead of the last message time.

Implemented Solution : For now let's just show the chat update time instead. We can think of something else next time