Steps to reproduce:

1. Create a blank presentation.
2. In the Title type two words e.g. "BOB, Continued"
3. Highlight and change the Font Size for the second part ", Continued" e.g.
make it half the font size
4. Now highlight the part "BOB" which is in the original font size
5. Press DEL to delete the "BOB" part
6. Press CTRL-Z for Undo

What happens is the whole title "BOB, Continued" assumes the font size of the ",
Continued" part. This incorrect, the "BOB" part should have been restored to its
original font size.