State: add additional missing checks on some message operations
State: add additional missing checks on some message operations

Some operations invoked by message selection mode (e.g. replying) didn't
adequately check the target message. This meant their behavior wasn't
consistent with the message selection binding hints about which actions
could be taken on a selected message. (E.g. the reply binding was not
shown by 'r' could still be used to reply to a message.)

matterhorn-chat/matterhorn,aisamanra/matterhorn