fix: add null safety checks for years in TopMovers

- Add || null to years array access to prevent undefined values
- Add !currentYear || !previousYear to insufficient data check
- This prevents errors when filtered data has less than 2 years

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

components/TopMovers.tsx

@@ -190,8 +190,8 @@ const TopMovers: React.FC<TopMoversProps> = ({ data, stockMap, vendorStockMap, b
   const { currentYear, previousYear, availableYears } = useMemo(() => {
     const years = Array.from(new Set(data.map(d => d.year))).sort((a: number, b: number) => b - a);
     return {
-      currentYear: years[0],
-      previousYear: years[1],
+      currentYear: years[0] || null,
+      previousYear: years[1] || null,
       availableYears: years
     };
   }, [data]);
@@ -263,7 +263,7 @@ const TopMovers: React.FC<TopMoversProps> = ({ data, stockMap, vendorStockMap, b
 
   }, [data, metric, currentYear, previousYear]);
 
-  if (availableYears.length < 2) {
+  if (availableYears.length < 2 || !currentYear || !previousYear) {
     return (
       <div className="flex flex-col items-center justify-center h-96 bg-slate-900 rounded-xl border border-border p-8">
         <h3 className="text-xl font-bold text-slate-300 mb-2">Insufficient Data for Comparison</h3>