Repeating post is marked as such even though a Repeat post is not created for it (due to be scheduled in the past)

A Repeat post is created only if date of a Repeating post + it's schedule is in the future.

When you setup a post to be a Repeating post with a schedule such that a Repeat post date happens to be in the past (read example below), the Repeat post is not created. However, the Repeating post is marked as `Repeating`. This is confusing!

**Solution**: an error message should be displayed in such case while trying to save a post with a Repeating schedule. That post won't be saved as `Repeating` post.

Example: main post (that we're wanting to set as a Repeating post) is published on the 10th October and we're setting it to be a `Daily` Repeating post. So a daily repeat post would have been scheduled for the 11th October. However, if present time (when we're saving changes) is anything past the 11th October, say the 12th October - then Repeat post date is in the past and therefore it is not published.