Update the index of the semicolon after truncating the line starting with a semicolon

[pzhlkj6612]

Hi. This project is great and thank you for your work.

I found an issue with string handling and tried to fix it. Please review and test the changes.

For testing

File v1.css:

selector {
    property_0:value_0;property_1:value_1
}

File v2.css is empty.

Output:

> .\CSSCompare.exe -v1 .\v1.css -v2 .\v2.css
selector{
        property_0:value_0
        p
        property_1:value_1
}

After applying the changes:

> .\CSSCompare.exe -v1 .\v1.css -v2 .\v2.css
selector{
        property_0:value_0
        property_1:value_1
}