[FF] Unable to apply block style on start of list item

[Garry Yao]

Reproducing Procedures

1. In Firefox, load the any of the sample page and clear up document content;
2. Press the 'Numbered List' command to create one list;
3. Keep cursor stay at the beginning of the newly created list item;
4. Open 'Format' combo and click on 'Heading1' style;

• Expected Result: You get 'Heading1' style opened inside the list item;
• Actual Result: List is removed and the block style is not applied too.

[Garry Yao]

WFM in trunk.