[NbtkTable] Correct variable type
[NbtkTable] Correct variable type

The variable has_expand_cols was wrongly a ClutterUnit array when it should
have been a gboolean array.

clutter-project/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx