chat-view: Create a new draft to save in history

chatty-history expects the content of the message to not change.
So instead of changing the content and resaving, create a new one
with empty content to avoid a possible crash as the history thread
may read the freed memory content otherwise

Fixes #737
10 jobs for wip/sadiq/fix-crash-saving-message in 15 minutes and 44 seconds (queued for 2 seconds)