Fix bug related to issue #187 (#205)

When deleting event categories, the user interface does not re-render correctly. This is caused by a missing key, and fixed by adding one.

Co-authored-by: = <=>

Author: ZoetjeZuurtje

src/settings/creator/Containers/events/CategoryContainer.svelte

@@ -51,7 +51,7 @@
         />
     {:else}
         <div class="existing-items">
-            {#each categories as category}
+            {#each categories as category (category.id)}
                 <div class="category">
                     <div use:name={category} />
                     <div class="color">