Fix issue with lazy loading

src/Carousel/Carousel.js

@@ -606,9 +606,9 @@ export class Carousel extends Base {
     }
 
     if (slide.$el) {
-      let curentIndex = parseInt(slide.$el.dataset.index, 10) || 0;
+      let curentIndex = slide.$el.dataset.index;
 
-      if (curentIndex !== slide.index) {
+      if (!curentIndex || parseInt(curentIndex, 10) !== slide.index) {
         slide.$el.dataset.index = slide.index;
 
         // Lazy load images

tests/3_carousel_test.js

@@ -644,4 +644,38 @@ describe("Carousel", function () {
 
     destroyInstance(instance);
   });
+
+  it("supports lazy loading", async function () {
+    const instance = createInstance({
+      markup: `<div class="carousel">
+        <div class="carousel__slide">
+          <img data-lazy-src="https://lipsum.app/id/1/300x200" />
+        </div>
+        <div class="carousel__slide">
+          <img data-lazy-src="https://lipsum.app/id/2/300x200" />
+        </div>
+        <div class="carousel__slide">
+          <img data-lazy-src="https://lipsum.app/id/3/300x200" />
+        </div>
+        <div class="carousel__slide">
+          <img data-lazy-src="https://lipsum.app/id/4/300x200" />
+        </div>
+        <div class="carousel__slide">
+          <img data-lazy-src="https://lipsum.app/id/5/300x200" />
+        </div>
+      </div>`,
+    });
+
+    let nodes = [...instance.$track.querySelectorAll("[data-lazy-src]")];
+
+    expect(nodes.length).to.equal(5);
+
+    expect(nodes[0].src).to.equal("https://lipsum.app/id/1/300x200");
+    expect(nodes[1].src).to.equal("https://lipsum.app/id/2/300x200");
+    expect(nodes[2].src).to.equal("");
+    expect(nodes[3].src).to.equal("");
+    expect(nodes[4].src).to.equal("https://lipsum.app/id/5/300x200");
+
+    destroyInstance(instance);
+  });
 });