Fixed grouped column Header that were not adjusting based on hidden child columns (#1381)
Fixed grouped column Header that were not adjusting based on hidden child columns (#1381)

* added assertion to check for show property inside column

* reverted previous change

* added a filter to weed out non-visible columns when calculating the size for grouped Headers

* added another case to the previous filter to factor in blank grouped Headers

react-tools/react-table,tannerlinsley/react-table