Fix: fix some crashes for people who have used dev at the same time and have the new theme-history

src/UI/BigComponents/ThemesList.svelte

@@ -14,6 +14,16 @@
   export let state: { osmConnection: OsmConnection }
   export let onlyIcons: boolean = false
   export let hasSelection: boolean = true
+  let themesFiltered: MinimalThemeInformation[] = []
+  for (const theme of themes) {
+    if (!theme) {
+      continue
+    }
+    if (themesFiltered.some(th => th.id === theme.id)) {
+      continue
+    }
+    themesFiltered.push(theme)
+  }
 </script>
 
 <section class="w-full">
@@ -23,7 +33,7 @@
       ? "flex flex-wrap items-center justify-center gap-x-2"
       : "theme-list my-2 gap-4 md:grid md:grid-flow-row md:grid-cols-2 lg:grid-cols-3"}
   >
-    {#each Utils.NoNull(themes) as theme (theme.id)}
+    {#each Utils.NoNull(themesFiltered) as theme (theme.id)}
       <ThemeButton {theme} {state} iconOnly={onlyIcons}>
         {#if $search && hasSelection && themes?.[0] === theme}
           <span class="thanks hidden-on-mobile" aria-hidden="true">