When you open the chat bar, you also use the default action of the item in hand.

When I was experimenting , i noticed something when I clicked the button and this is what happened:

What I thought would happen:
I would open the chat menu regularly.

What acually happened:

I found out that when you attempt to open the menu, you can either place a block, use a tool, or open a chest if the cross hair is alligned so.