fix: ImageViewer isLast attribute calculation error issue (#1902) (#2125)

Co-authored-by: yangyu8 <yangyu8@kingsoft.com>

packages/image-viewer/src/index.vue

@@ -144,7 +144,7 @@ export default defineComponent({
     })
 
     const isLast = computed(() => {
-      return index.value === 0
+      return index.value === props.urlList.length - 1
     })
 
     const currentImg = computed(() => {