Forwarded-To: https://gitlab.gnome.org/GNOME/evolution/issues/531

**Steps to reproduce:**

- I sent myself a plain text email containing a single line of text:

      abc

- When I received the email, I hit Ctrl-R to reply
- As per my configuration, Evolution opens a new plain-text compose window with
the email content quoted:

      On (time and date), Screwtapello wrote:
      > abc

- I select the text `abc` with my mouse
- I press the Delete key on my keyboard to delete it
- The "Undo" button on the toolbar becomes enabled, since an editing action has
been performed
- I click the "Undo" button on the toolbar to bring it back

**Actual results:**

- The "Undo" button becomes disabled, as though there's nothing to undo
- The deleted text does not reappear

**Expected results:**

- The deleted text reappears
- The "Undo" button becomes disabled, since there's nothing left to undo