修复错误

plugins/UserOnlineDevices/resources/views/admin-index.blade.php

@@ -307,7 +307,7 @@
             <input class="input" id="keyword" type="text" placeholder="Search by user ID or email">
             <select class="select" id="per-page">
                 @foreach ([20, 50, 100] as $size)
-                    <option value="{{ $size }}" @selected((int) $defaultPageSize === $size)>{{ $size }} / page</option>
+                    <option value="{{ $size }}" {{ ((int) $defaultPageSize === $size) ? 'selected' : '' }}>{{ $size }} / page</option>
                 @endforeach
             </select>
             <button class="btn primary" id="search-btn" type="button">Search</button>