bugfix: tree search pipe crashes when getchildren returns null

src/util/pipes/treeSearch.pipe.ts

@@ -8,7 +8,9 @@ export class TreeSearchPipe implements PipeTransform{
   public transform(array:any[]|null,filterFn:(item:any)=>boolean,getChildren:(item:any)=>any[]):any[]{
     const transformSingle = (item:any):boolean=>
       filterFn(item) ||
-      getChildren(item).some(transformSingle)
+      (getChildren(item)
+        ? getChildren(item).some(transformSingle)
+        : false)
     return array
       ? array.filter(transformSingle)
       : []