fix: prevent AttributeError for User users by skipping filter area creation

- Modified _create_widgets() to conditionally create filter area only for admin users
- Modified _create_filter_checkboxes() to return early for non-admin users
- This prevents AttributeError when accessing self.filter_frame for User users
- Admin users retain full filtering functionality
- Fixes the 'MaterialTypeManagementDialog' object has no attribute 'filter_frame' error

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

gui/material_type_management_dialog.py

@@ -385,10 +385,10 @@ class MaterialTypeManagementDialog(tk.Toplevel):
         main_container = ttk.Frame(self, padding=10)
         main_container.pack(fill=tk.BOTH, expand=True)
 
-        # 顶部：筛选区域
+        # 顶部：筛选区域 - 仅管理员可见
+        if self.session_manager.is_admin():
             filter_frame = ttk.LabelFrame(main_container, text="筛选（按负责人）", padding=10)
             filter_frame.pack(fill=tk.X, pady=(0, 10))
-
             self._create_filter_area(filter_frame)
 
         # 中部：数据表格
@@ -513,19 +513,16 @@ class MaterialTypeManagementDialog(tk.Toplevel):
 
     def _create_filter_checkboxes(self):
         """创建筛选复选框"""
+        # PERMISSION CHECK: 非管理员用户不创建筛选 UI
+        if not self.session_manager.is_admin():
+            self.managers = [self.session_manager.get_username()]
+            return
+
+        # 管理员：清空并重新创建复选框
         for widget in self.filter_frame.winfo_children():
             widget.destroy()
         self.manager_checkboxes.clear()
 
-        # PERMISSION CHECK: 非管理员用户隐藏筛选 UI
-        if not self.session_manager.is_admin():
-            self.managers = [self.session_manager.get_username()]
-            ttk.Label(
-                self.filter_frame,
-                text=f"仅显示您的数据（负责人：{self.session_manager.get_username()}）"
-            ).pack(anchor="w")
-            return
-
         # 管理员：获取所有负责人
         from db.materials_to_be_deleted_dao import MaterialsTypeToBeDeletedDAO
         dao = MaterialsTypeToBeDeletedDAO()