Copying a message without selecting anything does not work as expected

The following discussion from !142 (merged) should be addressed:

• @sebkur started a discussion: (+5 comments)

  I just tried this. Works nicely.

  One thing in non-optimal I think, but I'm not sure we can do anything about it: when I select some message partially or fully, right click + Copy puts the selected text into the clipboard. However if I do not select anything, the Copy action is still available from the context menu. When I select it, it puts the empty string into the clipboard. I think that's rather unexpected, I believe users could think that this would copy the whole message. I see two possible ways this could be better:

  1. when nothing is selected on the message, the Copy option is not visible or disabled
  2. when nothing is selected on the message, the Copy option copies the whole message text