PropTypes (oneOf) error when loading the Grid

[varga-boglarka]

Hi,

I found a very similar issue to #166.
I continuosly get the following error message in the browser console, as the grid has been loaded:

index.js:2178 Warning: Failed prop type: Invalid prop data of value [object Object] supplied to Grid, expected one of [null,null].

The solution might be using oneOfType instead of oneOf when defining the type of 'data' property.

The code is placed in components/Grid.jsx:
data: oneOf([ arrayOf(object), object, ]),

oneOf involves the EnumTypeChecker, while oneOfType involves UnionTypeChecker. Currently the EnumTypeChecker's validate method always fails and returns the mentioned error.