function toUniqueNormalizedIndices( indices, max ) {
	var hash;
	var out;
	var idx;
	var i;

	hash = {};
	out = [];
	for ( i = 0; i < indices.length; i++ ) {
		idx = normalizeIndex( indices[ i ], max );
		if ( idx < 0 ) {
			return null;
		}
		if ( hash[ idx ] === void 0 ) {
			hash[ idx ] = true;
			out.push( idx );
		}
	}
	return out;
}
Returns a list of unique indices after normalizing to the interval `[0,max]`.

@param {IntegerArray} indices - indices
@param {NonNegativeInteger} max - maximum index
@returns {(IntegerArray|null)} normalized indices

@example
var idx = toUniqueNormalizedIndices( [ -2, 5 ], 10 );
// returns [ 9, 5 ]

idx = toUniqueNormalizedIndices( [ 15 ], 10 );
// returns null