New check for block-level-elements

When a tag is removed inside the same tag with an extra space in the end of the tag, then a <br> tag is added, even if the tag is a non-block-element.
For example: inside <sup>example <sup>, if you select "example" without the succeeding space and remove the upper case, then a <br> tag will be added.
The fix checks if the operation is within a block-level-element and does not add the <br> if it's not a block-level-element.