Describe the bug

After uploading an image to an existing gallery via the button that appears under the gallery images, this image is not listed in the edit gallery view. I am using Gutenberg 3.5.0.

To Reproduce

Steps to reproduce the behavior:

1. Create a gallery block and select images from the media library for it.
2. Upload an additional image via the button under the gallery images.
3. Click the Edit Gallery button.
4. See that the uploaded image is not listed as a selected image.

Expected behavior

The uploaded image should be listed as part of the gallery.

Screenshots

Desktop (please complete the following information):

• Windows 10
• Firefox Nightly
• Version 63.0a1 (2018-08-16)