fix: safeguard ThreeSixtyViewer metadata.json frames load against undefined

src/components/ThreeSixtyViewer.vue

@@ -170,11 +170,9 @@ const startPreloading = async () => {
     console.log("No metadata.json found or failed to load. Falling back to default turntable.", e);
   }
 
-  if (meta) {
+  if (meta && meta.frames && meta.frames.length) {
     projectMetadata.value = meta;
-    if (meta.frames && meta.frames.length) {
-      totalFramesCount.value = meta.frames.length;
-    }
+    totalFramesCount.value = meta.frames.length;
 
     // Sync angles from the first frame's vector
     if (meta.frames[0] && meta.frames[0].vector) {
@@ -217,6 +215,12 @@ const startPreloading = async () => {
     });
   } else {
     // Fallback: 1D horizontal turntable
+    if (meta) {
+      projectMetadata.value = meta;
+      if (meta.frames_count) {
+        totalFramesCount.value = meta.frames_count;
+      }
+    }
     let loaded = 0;
     const list: HTMLImageElement[] = [];