Prevent spurious error (#14796)

* Simple fix

* Suggestions

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/webhook_test.go

@@ -798,4 +798,14 @@ func TestDoOutgoingWebhookRequest(t *testing.T) {
 		require.NotNil(t, err)
 		require.IsType(t, &url.Error{}, err)
 	})
+
+	t.Run("without response", func(t *testing.T) {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		}))
+		defer server.Close()
+
+		resp, err := th.App.doOutgoingWebhookRequest(server.URL, strings.NewReader(""), "application/json")
+		require.Nil(t, err)
+		require.Nil(t, resp)
+	})
 }

model/outgoing_webhook.go

@@ -112,6 +112,9 @@ func (o *OutgoingWebhookResponse) ToJson() string {
 func OutgoingWebhookResponseFromJson(data io.Reader) (*OutgoingWebhookResponse, error) {
 	var o *OutgoingWebhookResponse
 	err := json.NewDecoder(data).Decode(&o)
+	if err == io.EOF {
+		return nil, nil
+	}
 	return o, err
 }