Merge pull request #26 from Neovici/hideFromRootPartUndefined

Undefined check in _computeHideFromRoot

cosmoz-omnitable-treenode-column.html

@@ -286,7 +286,7 @@
 
 			const paths = values.map(value => this.getPathByProperty(this.keyProperty, value, ownerTree)),
 				reducedPaths = paths.reduce((agg, part) => {
-					if (agg === undefined || part.length < agg.length) {
+					if (agg === undefined || part !== undefined && part.length < agg.length) {
 						return part;
 					}
 					return agg;