add exception message

fet2020/finance/admin.py

@@ -185,6 +185,7 @@ class BillAdmin(admin.ModelAdmin):
         except Exception:
             return "-"
 
+        try:
             qrcode = helpers.make_epc_qr(
                 name=tmp.name,
                 iban=tmp.iban,
@@ -193,6 +194,9 @@ class BillAdmin(admin.ModelAdmin):
                 bic=tmp.bic,
                 encoding="utf-8",
             )
+        except Exception:
+            return "Daten für QR Code ungültig"
+
         uri = qrcode.png_data_uri(scale=3.0)
         return format_html(f'<img src="{uri}">')