Check for nil value on AvailableWebhooks.

plugins/inputs/webhooks/webhooks.go

@@ -75,9 +75,11 @@ func (wb *Webhooks) AvailableWebhooks() []Webhook {
 		f := s.Field(i)
 
 		if wbPlugin, ok := f.Interface().(Webhook); ok {
+			if !reflect.ValueOf(wbPlugin).IsNil() {
 				webhooks = append(webhooks, wbPlugin)
 			}
 		}
+	}
 
 	return webhooks
 }

plugins/inputs/webhooks/webhooks_test.go

@@ -0,0 +1,29 @@
+package webhooks
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/influxdata/telegraf/plugins/inputs/webhooks/github"
+	"github.com/influxdata/telegraf/plugins/inputs/webhooks/rollbar"
+)
+
+func TestAvailableWebhooks(t *testing.T) {
+	wb := NewWebhooks()
+	expected := make([]Webhook, 0)
+	if !reflect.DeepEqual(wb.AvailableWebhooks(), expected) {
+		t.Errorf("expected to %v.\nGot %v", expected, wb.AvailableWebhooks())
+	}
+
+	wb.Github = &github.GithubWebhook{Path: "/github"}
+	expected = append(expected, wb.Github)
+	if !reflect.DeepEqual(wb.AvailableWebhooks(), expected) {
+		t.Errorf("expected to be %v.\nGot %v", expected, wb.AvailableWebhooks())
+	}
+
+	wb.Rollbar = &rollbar.RollbarWebhook{Path: "/rollbar"}
+	expected = append(expected, wb.Rollbar)
+	if !reflect.DeepEqual(wb.AvailableWebhooks(), expected) {
+		t.Errorf("expected to be %v.\nGot %v", expected, wb.AvailableWebhooks())
+	}
+}