fix : 问题详情中找不到企业时报错

lib/app/features/problem/presentation/controllers/problem_form_controller.dart

@@ -31,8 +31,9 @@ class ProblemFormController extends GetxController {
     return formMode == FormMode.view;
   }
 
-  Enterprise get enterprise {
-    return enterpriseList.firstWhere(
+  // TODO : 这里可能会有问题，企业列表为空时会报错
+  Enterprise? get enterprise {
+    return enterpriseList.firstWhereOrNull(
       (enterprise) => enterprise.id == problem!.enterpriseId,
     );
   }

lib/app/features/problem/presentation/pages/problem_form_page.dart

@@ -459,7 +459,7 @@ class ProblemFormPage extends GetView<ProblemFormController> {
                 left: 16.w,
                 right: 16.w,
               ),
-              child: Text(controller.enterprise.name),
+              child: Text(controller.enterprise?.name ?? "未知企业"),
             )
           else
             Padding(