Toggling an unordered list twice inside a blockquote allows nesting of blockquote

[mitermayer]

Steps:

1. Click "Blockquote"
2. Click "UL"
3. Click "UL"
4. Click "UL"
5. Click "UL"
6. Click "Blockquote"

I would have expected that the final click of "Blockquote" would remove the blockquote rather than nested another one.