_color being null if border tag is empty

[hassoon3]

Hi,

In a generated excel file by a DevExpress library, there might be some border tags in the style that have no content. Reading like this (intended tag in bold):

    <borders count="2">
        **<border />**
        <border>
            <left/>
            <right/>
            <top/>
            <bottom style="thin">
                <color indexed="64"/>
            </bottom>
            <diagonal/>
        </border>
    </borders>

In which case an NullReferenceException will be thrown when accessing _color.Copy()

The recommended and tested solution is to check for the Exists property before trying to copy the color.

I am sorry for not including a Unit Test, as I am still not so fluent in writing them in .Net

Regards,

[supertx2]

This, and adding a question mark on get Id in ExcelBorderItemXml.cs will solve my issue with telerik Reporting, #524