Patched gallery duplication on multi-image upload

Quick patch to clear the gallery display when getting the first page.
Duplication of the galler was occuring due to the mulitple upload events
loading the gallery mulitple times while only clearing the existing
gallery at the start of all refreshes.

A bit flashy in terms of user experience, as there will still be
mulitple load/clear events but fixes the duplication. Could be done more
elegently in future by communicating up image upload counts.

For #3160

resources/js/components/image-manager.js

@@ -122,6 +122,9 @@ class ImageManager {
         };
 
         const {data: html} = await window.$http.get(`images/${this.type}`, params);
+        if (params.page === 1) {
+            this.listContainer.innerHTML = '';
+        }
         this.addReturnedHtmlElementsToList(html);
         removeLoading(this.listContainer);
     }