fix: react hook

src/components/timeline/CategorySelector.tsx

@@ -73,15 +73,6 @@ export const CategorySelector: React.FC<CategorySelectorProps> = ({
     }
   }, [isOpen, onCancel])
 
-  // 自动聚焦
-  React.useEffect(() => {
-    if (isOpen && dropdownRef.current) {
-      dropdownRef.current.focus()
-    }
-  }, [isOpen])
-
-  if (!isOpen) return null
-
   // 计算下拉框位置，确保不超出视窗
   const adjustedPosition = React.useMemo(() => {
     const maxHeight = 300 // 下拉框最大高度
@@ -102,6 +93,16 @@ export const CategorySelector: React.FC<CategorySelectorProps> = ({
     return { x: Math.max(padding, x), y: Math.max(padding, y) }
   }, [position])
 
+  // 自动聚焦
+  React.useEffect(() => {
+    if (isOpen && dropdownRef.current) {
+      dropdownRef.current.focus()
+    }
+  }, [isOpen])
+
+  // 如果不显示，返回 null
+  if (!isOpen) return null
+
   const dropdown = (
     <div
       ref={dropdownRef}