center on/highlight marker for views with argument with multiple values

If the Node ID argument of the view accepts multiple values then "Center on node argument" and "Highlight marker for node argument" won't work anymore. And that's because the argument will be a list of NodeIDs, separated with "," or "+", something like "1+2+3" or "1,2,3".

Attached you'll find a patch (for 6.x-1.x-dev) that fixes this issue by using the first node in the list for the center/highlight.