libcacard: Fix wrong assertion (reported by cppcheck)

assert("...") will never do anything. This assertion handles a case
which should never occur, so it must be assert(!"...").

Cc: Alon Levy <alevy@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>

libcacard/card_7816.c

@@ -754,7 +754,7 @@ vcard_process_apdu(VCard *card, VCardAPDU *apdu, VCardResponse **response)
         return vcard7816_vm_process_apdu(card, apdu, response);
     case VCARD_DIRECT:
         /* if we are type direct, then the applet should handle everything */
-        assert("VCARD_DIRECT: applet failure");
+        assert(!"VCARD_DIRECT: applet failure");
         break;
     }
     *response =