Small bugs (#1324)
* initialise gallery images to None, fix icon
* dispatch submit event when pressing return on 1 line textbox
* Update ui/packages/app/src/components/Gallery/Gallery.svelte
* Update ui/packages/app/src/components/Gallery/Gallery.svelte
Co-authored-by: Abubakar Abid <abubakar@huggingface.co>
