Attempting to open a table that is missing a header will crash grunti

[rohrlich]

Would be good if this could be detected so a dialog could be displayed.

2021/03/25 19:17:44 Warning: etable.Table has multiple columns with same name!
[0 -1 0.0301 0.9188 0.08122 0 0 0.2877 0 0 0.279 0 0 0.2553 0 0 0.2834 0 0 0.2898 0.04003 0.03625 0.0463 0.04377 0.07658 0 0.417 0 0.4707 0 0.336 0.0003333 0.4077 0 0.4889 0 0.3671 0 0.516 0 0.4179 0 0.2016 0 0.1866]
panic: interface conversion: ki.Ki is *gi.Label, not *gi.Action

goroutine 5 [running]:
github.com/emer/etable/etview.(*TableView).ConfigSliceGrid(0xc017098000)
/Users/rohrlich/go/src/github.com/emer/etable/etview/tableview.go:318 +0x33a8
github.com/emer/etable/etview.(*TableView).Config(0xc017098000)
/Users/rohrlich/go/src/github.com/emer/etable/etview/tableview.go:147 +0x287
github.com/emer/etable/etview.(*TableView).TableConfig(0xc017098000)
/Users/rohrlich/go/src/github.com/emer/etable/etview/tableview.go:107 +0x245
github.com/emer/etable/etview.(*TableView).SetTable(0xc017098000, 0xc012559b80, 0x0, 0x0)
/Users/rohrlich/go/src/github.com/emer/etable/etview/tableview.go:63 +0xae