添加职位分类相关接口：获取职位分类列表；

app/JsonRpc/NewsService.php

@@ -2055,8 +2055,13 @@ class NewsService implements NewsServiceInterface
             }
             $zwids = array_values(array_unique($child_zwids));
         }
-        $count =  JobPosition::whereIn('zwid', $zwids)->count();
-        $position =  JobPosition::whereIn('zwid', $zwids)
+        $zwids = $zwids ?? null;
+        $count =  JobPosition::when(!empty($zwids), function ($query) use ($zwids) {
+            $query->whereIn('zwid', $zwids);
+        })->count();
+        $position =  JobPosition::when(!empty($zwids), function ($query) use ($zwids) {
+            $query->whereIn('zwid', $zwids);
+        })
         ->offset(($page - 1) * $page_size)
         ->limit($page_size)->get()
         ->map(function ($item) use ($data) {