UI: don't show 'open image on website' if it is not defined

src/UI/Image/AttributedImage.svelte

@@ -26,7 +26,7 @@
 
   export let image: Partial<ProvidedImage> & { id: string; url: string }
   let fallbackImage: string = undefined
-  if (image.provider === Mapillary.singleton) {
+  if (image?.provider === Mapillary.singleton) {
     fallbackImage = "./assets/svg/blocked.svg"
   }
 
@@ -41,7 +41,7 @@
     | Store<Feature<Geometry, HotspotProperties>[]> = []
 
   let loaded = false
-  let visitUrl = image.provider.visitUrl(image)
+  let visitUrl = image.provider?.visitUrl(image)
   let showBigPreview = new UIEventSource(false)
   onDestroy(
     showBigPreview.addCallbackAndRun((shown) => {
@@ -115,10 +115,12 @@
       {#if $$slots["dot-menu-actions"] || visitUrl !== undefined}
         <DotMenu dotsPosition="top-0 left-0 absolute" hideBackground>
           <slot name="dot-menu-actions" />
+          {#if visitUrl !== undefined}
           <a href={visitUrl} target="_blank" rel="noopener">
             <ExternalLinkIcon class="w-6" />
             <Tr t={Translations.t.image.openOnWebsite.Subs(image.provider)} />
           </a>
+          {/if}
         </DotMenu>
       {/if}
       {#if !loaded}