more nfc

main.py

@@ -106,14 +106,17 @@ class CliInteraction(UserInteraction):
         return True
 
 def read_nfc_tag():
+    clf = None
     try:
         clf = nfc.ContactlessFrontend('usb')
         tag = clf.connect(rdwr={'on-connect': lambda tag: False})
-        clf.close()
         return tag.identifier if tag else None
     except Exception as e:
         print("NFC read error:", e)
         return None
+    finally:
+        if clf:
+            clf.close()
 
 
 while True: