Fix empty scope.nodes causing 400 Bad Request

When no nodes are selected, use wildcard ['*'] instead of empty array
to match the documented behavior ("No selected Nodes means All Nodes").

Fixes netdata/netdata-cloud#1132

Author: ktsaou

src/shared/hooks/useGetChartData.ts

@@ -60,7 +60,7 @@ export const useGetChartData = async ({
       options: ['jsonwrap', 'flip', 'ms'],
       scope: {
         contexts: [contextId],
-        nodes,
+        nodes: nodes.length ? nodes : ['*'],
         dimensions,
         labels,
       },