slight database mixup fix

Web/app.py

@@ -9108,13 +9108,17 @@ def admin_add_invoice_correction(borrow_id):
 def library_item_invoices(item_id):
     """Show all stored invoices for one specific library item."""
     if 'username' not in session:
-        flash('Ihnen ist es nicht gestattet auf dieser Internetanwendung, die eben besuchte Adrrese zu nutzen, versuchen sie es erneut nach dem sie sich mit einem berechtigten Nutzer angemeldet haben!', 'error')
+        flash(
+            'Ihnen ist es nicht gestattet auf dieser Internetanwendung, die eben besuchte Adrrese zu nutzen, versuchen sie es erneut nach dem sie sich mit einem berechtigten Nutzer angemeldet haben!',
+            'error')
         return redirect(url_for('login'))
+
     if not cfg.MODULES.is_enabled('library'):
         flash('Bibliotheks-Modul ist deaktiviert.', 'error')
         return redirect(url_for('home_admin'))
+
     current_permissions = us.get_effective_permissions(session['username'])
-                
+
     if not current_permissions['pages'].get('library_loans_admin', False):
         flash('Ihnen fehlen die nötigen Berechtigungen, um diese Aktion auszuführen.', 'error')
         return redirect(url_for('library_view'))
@@ -9135,9 +9139,12 @@ def library_item_invoices(item_id):
             flash('Bibliotheksmedium nicht gefunden.', 'error')
             return redirect(url_for('library_loans_admin'))
 
+        item_id_obj = item_doc.get('_id')
+        item_id_str = str(item_id_obj)
+
         borrow_docs = list(ausleihungen.find(
             {
-                'Item': str(item_doc.get('_id')),
+                'Item': {'$in': [item_id_str, item_id_obj]},
                 'InvoiceData': {'$exists': True, '$ne': {}}
             },
             {
@@ -9152,19 +9159,27 @@ def library_item_invoices(item_id):
         entries = []
         for borrow_doc in borrow_docs:
             invoice_data = borrow_doc.get('InvoiceData') or {}
+
             created_at = invoice_data.get('created_at')
-            created_at_display = created_at.strftime('%d.%m.%Y %H:%M') if isinstance(created_at, datetime.datetime) else (str(created_at) if created_at else '')
+            created_at_display = created_at.strftime('%d.%m.%Y %H:%M') if isinstance(created_at,
+                                                                                     datetime.datetime) else (
+                str(created_at) if created_at else '')
+
             paid_at = invoice_data.get('paid_at')
-            paid_at_display = paid_at.strftime('%d.%m.%Y %H:%M') if isinstance(paid_at, datetime.datetime) else (str(paid_at) if paid_at else '')
+            paid_at_display = paid_at.strftime('%d.%m.%Y %H:%M') if isinstance(paid_at, datetime.datetime) else (
+                str(paid_at) if paid_at else '')
 
             entries.append({
                 'borrow_id': str(borrow_doc.get('_id')),
                 'borrow_status': borrow_doc.get('Status', ''),
                 'borrow_user': borrow_doc.get('User', ''),
-                'borrow_start': borrow_doc.get('Start').strftime('%d.%m.%Y %H:%M') if isinstance(borrow_doc.get('Start'), datetime.datetime) else '',
-                'borrow_end': borrow_doc.get('End').strftime('%d.%m.%Y %H:%M') if isinstance(borrow_doc.get('End'), datetime.datetime) else '',
+                'borrow_start': borrow_doc.get('Start').strftime('%d.%m.%Y %H:%M') if isinstance(
+                    borrow_doc.get('Start'), datetime.datetime) else '',
+                'borrow_end': borrow_doc.get('End').strftime('%d.%m.%Y %H:%M') if isinstance(borrow_doc.get('End'),
+                                                                                             datetime.datetime) else '',
                 'invoice_number': invoice_data.get('invoice_number', ''),
-                'invoice_amount': _format_money_value(invoice_data.get('amount')),
+                'invoice_amount': _format_money_value(invoice_data.get('amount')) if hasattr(invoice_data,
+                                                                                             'get') else '0,00',
                 'invoice_reason': invoice_data.get('damage_reason', ''),
                 'invoice_created_at': created_at_display,
                 'invoice_created_by': invoice_data.get('created_by', ''),
@@ -9187,6 +9202,7 @@ def library_item_invoices(item_id):
             student_cards_module_enabled=cfg.MODULES.is_enabled('student_cards'),
             mail_module_enabled=cfg.MODULES.is_enabled('mail')
         )
+
     except Exception as e:
         app.logger.error(f"Error loading invoice history for item {item_id}: {e}")
         flash('Fehler beim Laden der Rechnungshistorie.', 'error')
@@ -9195,7 +9211,6 @@ def library_item_invoices(item_id):
         if client:
             client.close()
 
-
 @app.route('/admin_reset_user_password', methods=['POST'])
 def admin_reset_user_password():
     """