This problem happens on Ubuntu Linux and HTMLEditor only, it's fine for TextArea/TextField on Ubuntu.

Steps to reproduce:
1. On a HTMLEditor, switch on CCJK input method.
2. Compose something, but do not commit the composing text.
3. Press backspace to delete all the partial composing text.
4. try to compose again

Bug: the compose text is committed directly, which means the input method is deactivated.
Workaround: change focus to another editable filed then change focus back to HTMLEditor, the input method works again.