fix(Permalink): prevent Permalink crash when a layer has no children attribute (#736)

Author: danji90

src/components/Permalink/Permalink.js

@@ -116,7 +116,7 @@ class Permalink extends PureComponent {
           } else if (
             !isBaseLayer(l) &&
             !isLayerHidden(l) &&
-            !(l.children || l.get("children")).some((ll) => {
+            !(l.children || l.get("children"))?.some((ll) => {
               return ll.getVisible ? ll.getVisible() : ll.visible;
             })
           ) {