Adding check and default to legend component

Author: simianhacker

x-pack/plugins/infra/public/pages/metrics/inventory_view/components/waffle/legend.tsx

@@ -17,7 +17,11 @@ import {
 import { GradientLegend } from './gradient_legend';
 import { LegendControls } from './legend_controls';
 import { StepLegend } from './steps_legend';
-import { useWaffleOptionsContext, WaffleLegendOptions } from '../../hooks/use_waffle_options';
+import {
+  DEFAULT_LEGEND,
+  useWaffleOptionsContext,
+  WaffleLegendOptions,
+} from '../../hooks/use_waffle_options';
 import { SteppedGradientLegend } from './stepped_gradient_legend';
 interface Props {
   legend: InfraWaffleMapLegend;
@@ -52,7 +56,7 @@ export const Legend: React.FC<Props> = ({ dataBounds, legend, bounds, formatter
   return (
     <LegendContainer>
       <LegendControls
-        options={legendOptions}
+        options={legendOptions != null ? legendOptions : DEFAULT_LEGEND}
         dataBounds={dataBounds}
         bounds={bounds}
         autoBounds={autoBounds}