title: UITableViewCells invalid context trying to draw
body: <p>I am trying to draw a checkbox triangle in a UITableViewCell.
  In the Data Source protocol method -tableView:cellForRowAtIndexPath: I have added the following in the code bloc which asks if the cell is nil:</p>
  
  <pre><code>    CGContextRef context = UIGraphicsGetCurrentContext(); 
      CGContextBeginPath(context);
      CGContextMoveToPoint(context, 75,10);
      CGContextAddLineToPoint(context, 10, 150);
      CGContextAddLineToPoint(context, 160, 150);
      CGContextClosePath(context);
      [[UIColor blackColor] setStroke];
      CGContextStrokePath(context);
  </code></pre>
  
  <p>When executing the code, I get a series of 'invalid context 0x0' messages on the following methods:
  CGContextBeginPath:
  CGContextMoveToPoint:
  CGContextAddLineToPoint: (twice)
  CGContextClosePath:
  CGContextSetStrokeColorWithColor:
  CGContextDrawPath</p>
  
  <p>The messages repeat for each TableViewCell row in my table.</p>
  
  <p>Am I not able to draw triangles or other geometric shapes within customizedUITableViewCell objects?</p>