Fixes two bugs related to opening an ObjectPanel when there is no data flowing in.  The first caused the panel to not draw itself correctly until the mouse moved over it.  The second caused an issue where requesting a graph would hang the application.  Finally, also fixes an issue where axis ranges were computed incorrectly when there was only one point on the graph.
Cleanup on code path that should never be used, now safer and prints a warning.
Merge pull request #2 from andybarry/master

Fixes two bugs related to opening an ObjectPanel when there is no data flowing in