Images sent automatically with no warning

[Elaborendum]

Pasting an image from the clipboard on the "send a message" screen causes it to be sent as soon as it's pasted.

I looked around and, according to #108, it seems to be intended. Regardless, I think a small warning would be nice, specially since the pasted image doesn't fully appear in the sender's side if it's too big and could result in the wrong image being sent.

I don't usually use apps like these, so maybe this is just a normally expected feature in these and needs no warning.