Fix an issue about bold/italic toggling with CJK

[Pisces000221]

Before this change, we can only remove bold attribute of whole words.

This is a **bold** text

We select the word 'bold', click the 'bold' button and everything is okay.

This is a bold text

However, in Chinese/Japanese/Korean we don't have spaces between words.

No**spaces**between words in CJK

Therefore, selecting 'spaces' and clicking the 'bold' button will not work properly. It becomes

Nospaces**between words in CJK

I fixed this and it worked well for both Latin and CJK characters. Please take a look if possible. Thanks!