bearer-qmi: app specific info in PCO may be empty

  ModemManager[562783]: <err> [1673538458.350130] mm_utils_bin2hexstr: assertion 'bin != NULL' failed
  ModemManager[562783]: <dbg> [1673538458.350167] [modem0/bearer0] container ID: 0
  ModemManager[562783]: <dbg> [1673538458.350201] [modem0/bearer0] app specific info: (null)

Treat it better by only trying to build the app specific info string
if there are contents in the array.
1 file changed