fix(imageview): Don't try to load unresolved images

Signed-off-by: Joas Schilling <coding@schilljs.com>

src/nodes/ImageView.vue

@@ -243,6 +243,11 @@ export default {
 	methods: {
 		async loadPreview() {
 			this.attachment = await this.$attachmentResolver.resolve(this.src)
+			if (!this.attachment.previewUrl) {
+				this.loaded = true
+				this.failed = true
+				return
+			}
 			return new Promise((resolve, reject) => {
 				const img = new Image()
 				img.onload = async () => {