[Bug] plot.items not being cleared after each frame.

[lawabider]

Bug description
In a simple plot which has a new title in each frame, plot.items quickly increased in size.
Perhaps we should add gp.CurrentItems->Reset() to EndPlot() after "CLEANUP":

   // CLEANUP ----------------------------------------------------------------   

   // remove items
   if (gp.CurrentItems == &plot.Items)
   {
       gp.CurrentItems->Reset(); // I added this.
      gp.CurrentItems = nullptr;
   }