title: TCrossFunction not consistent with TLineSeries when ValueColor = clNone
body: <p>When plotting a line series in which some values have their ValueColor set to clNone, the line will display as if those points didn't exist or were invisible.</p>
  
  <p>However, when I use the TCrossFunction  against that same line series, it behaves as if those points were visible.</p>
  
  <p>The first image shows the crosspoints indicated by the orange 'X' symbols when the ValueColor of the point between them is NOT clNone.</p>
  
  <p><img src="https://i.stack.imgur.com/hf6sJ.jpg" alt="enter image description here"></p>
  
  <p>This image shows the crosspoints are still in the same location, even though the point between them has had its ValueColor property set to clNone.</p>
  
  <p><img src="https://i.stack.imgur.com/26xnP.jpg" alt="enter image description here"></p>
  
  <p>BTW, I did call CheckDataSource to refresh the crosspoints before plotting.</p>
  
  <p>How do I get the crosspoints function to respect the ValueColor property?</p>