IE : Numbered list can not be converted to bulleted list or vice versa

[Satya Minnekanti]

To reproduce the defect:

1. Open any CK Editor sample and create a numbered list

2. Select all the list items in numbered list and click on Bulleted list icon in the Tool bar

Expected Result: Numbered list is converted to Bulleted list.

Actual Result: Numbered list not converted to bulleted list and we are getting an error. and the error is 'this.$currentStyle is null or not an object'

Same issue happens when we try to convert Bulleted list to Numbered list

[Frederico Caldeira Knabben]

DUP of #8284.