* in preferences viewers, a 0 value for samples should be detected and
  flagged as invalid
* on Linux (and possibly other platforms), graphs are not stable with
  BLT 2.4h and core dumps may occur after adding or removing cells
* fix empty element label problem in viewer when loading from a
  asynchronous module save file: update labels at each poll?
* pies shows doubled / slanted 0 line sometimes when resizing
* in dnd stacked drops sites show highlighting residue when cursor is
  hovering over

