Guard against nil pointer dereference (elastic#8107)

* Add nil guard

* Return if nil

* Use the assert.CollectT object

Author: ycombinator

testing/integration/beat_receivers_test.go

@@ -280,6 +280,7 @@ func TestAgentMonitoring(t *testing.T) {
 
 			// we should have filebeatreceiver and metricbeatreceiver running
 			otelCollectorStatus := status.Collector
+			require.NotNil(collect, otelCollectorStatus)
 			assert.Equal(collect, int(cproto.CollectorComponentStatus_StatusOK), otelCollectorStatus.Status)
 			pipelineStatusMap := otelCollectorStatus.ComponentStatusMap