KH20 Rim (2007) - Crack or Seam

I Have a KH20 07 and there is a thin, perfectly straight line, seperating the rim. There is a tiny gap in the rim. Is this a seam or a crack, I thought it might be a seam because the line is perfectly srtaight. I hope ist not a crack! If is is do I need a new rim, or can I keep riding this one. I ride trials, and my biggest drop is about 4.5 ft.
thanks Cameron:)