diff --git a/api/bulk_operation.php b/api/bulk_operation.php
index 0d42085..4295099 100644
--- a/api/bulk_operation.php
+++ b/api/bulk_operation.php
@@ -49,10 +49,10 @@ if (!$operationType || empty($ticketIds)) {
     exit;
 }
 
-// Validate ticket IDs are positive integers
+// Validate ticket IDs: must be non-empty numeric strings (allows leading zeros)
 $ticketIds = array_values(array_filter(array_map(function($id) {
-    $int = (int)$id;
-    return ($int > 0 && (string)$int === (string)$id) ? $int : null;
+    $s = trim((string)$id);
+    return (ctype_digit($s) && (int)$s > 0) ? $s : null;
 }, $ticketIds)));
 if (empty($ticketIds)) {
     echo json_encode(['success' => false, 'error' => 'No valid ticket IDs provided']);
diff --git a/controllers/DashboardController.php b/controllers/DashboardController.php
index caa02d5..0b2908e 100644
--- a/controllers/DashboardController.php
+++ b/controllers/DashboardController.php
@@ -186,6 +186,10 @@ class DashboardController {
         $categories = [];
         $types = [];
 
+        if (!$result) {
+            return ['categories' => $categories, 'types' => $types];
+        }
+
         while ($row = $result->fetch_assoc()) {
             if ($row['field'] === 'category' && !in_array($row['value'], $categories, true)) {
                 $categories[] = $row['value'];
diff --git a/models/TicketModel.php b/models/TicketModel.php
index 31821d0..7a1f7fc 100644
--- a/models/TicketModel.php
+++ b/models/TicketModel.php
@@ -558,8 +558,8 @@ class TicketModel {
             return [];
         }
 
-        // Sanitize ticket IDs
-        $ticketIds = array_map('intval', $ticketIds);
+        // Sanitize ticket IDs: cast to string to preserve leading zeros
+        $ticketIds = array_map('strval', $ticketIds);
 
         // Create placeholders for IN clause
         $placeholders = str_repeat('?,', count($ticketIds) - 1) . '?';
@@ -578,7 +578,7 @@ class TicketModel {
                 WHERE t.ticket_id IN ($placeholders)";
 
         $stmt = $this->conn->prepare($sql);
-        $types = str_repeat('i', count($ticketIds));
+        $types = str_repeat('s', count($ticketIds));
         $stmt->bind_param($types, ...$ticketIds);
         $stmt->execute();
         $result = $stmt->get_result();