add school year model

app/Services/Administrator/TeacherSubmissionSupportService.php

@@ -83,8 +83,21 @@ class TeacherSubmissionSupportService
             : mb_substr($text, 0, $limit) . '…';
     }
 
-    public function parseMissingItemsPayload(string $payload): array
+    public function parseMissingItemsPayload($payload): array
     {
+        if (is_array($payload)) {
+            $items = [];
+            foreach ($payload as $item) {
+                $item = trim((string) $item);
+                if ($item !== '') {
+                    $items[] = $item;
+                }
+            }
+
+            return array_values(array_unique($items));
+        }
+
+        $payload = trim((string) $payload);
         if ($payload === '') {
             return [];
         }