prevent IntersectionObserver error on unobserve with null ref

src/pages/Gallary/ImageGallary.jsx

@@ -106,24 +106,27 @@ const ImageGallery = () => {
     return () => eventBus.off("image_gallery", handler);
   }, [selectedProjectId, refetch]);
 
-  useEffect(() => {
-    if (!loaderRef.current) return;
-    const obs = new IntersectionObserver(
-      ([entry]) => {
-        if (
-          entry.isIntersecting &&
-          hasNextPage &&
-          !isFetchingNextPage &&
-          !isLoading
-        ) {
-          fetchNextPage();
-        }
-      },
-      { rootMargin: "200px", threshold: 0.1 }
-    );
-    obs.observe(loaderRef.current);
-    return () => obs.unobserve(loaderRef.current);
-  }, [hasNextPage, isFetchingNextPage, isLoading, fetchNextPage]);
+useEffect(() => {
+  if (!loaderRef.current) return;
+
+  const observer = new IntersectionObserver(
+    ([entry]) => {
+      if (entry.isIntersecting && hasNextPage && !isFetchingNextPage && !isLoading) {
+        fetchNextPage();
+      }
+    },
+    { rootMargin: "200px", threshold: 0.1 }
+  );
+
+  observer.observe(loaderRef.current);
+
+  return () => {
+    if (loaderRef.current) {
+      observer.unobserve(loaderRef.current); 
+    }
+  };
+}, [hasNextPage, isFetchingNextPage, isLoading, fetchNextPage]);
+
 
   // Utility: derive filter options
   const getUniqueValues = useCallback(