title: ERROR Invalid coordinate in positionRelativeToViewPoint:forCoordinate:inDirection
body: <p>For some reason all of a sudden I get an error when making graphs with coreplot.
  In the method</p>
  
  <pre><code>-(void)positionRelativeToViewPoint:(CGPoint)point forCoordinate:(CPTCoordinate)coordinate inDirection:(CPTSign)direction
  </code></pre>
  
  <p>the direction becomes invalid (it is not a CPTSignNone, CPTSignNegative nor CPTSignPositive). 
  My code can be found on Github (<a href="https://github.com/anneEverars/Vittles" rel="nofollow">https://github.com/anneEverars/Vittles</a>).</p>
  
  <p>Does anyone have an idea to solve this?</p>