[PATCH] mm-modem-helpers-qmi: avoid SIGSEGV with mmcli --set-current-bands

[Nick]

Some further information:  It seems if I try to set any band above 28, such as eutran-32 the command fails.  This is on a MC7430.

Command
~# mmcli -m 0 --set-current-bands="eutran-3|eutran-5|eutran-7|eutran-8|eutran-18|eutran-19|eutran-21|eutran-28|utran-1|utran-6|utran-9|utran-19|eutran-32"
~# error: couldn't set current bands: 'GDBus.Error:org.freedesktop.libqmi.Error.Protocol.Internal: Couldn't set system selection preference: QMI protocol error (3): 'Internal''

Debug output:
Tue Aug 20 14:57:23 2019 daemon.debug [7565]: <debug> [1566277043.625021] Setting new list of bands: 'eutran-3, eutran-5, eutran-7, eutran-8, eutran-18, eutran-19, eutran-21, eutran-28, utran-1, utran-6, utran-9, utran-19, eutran-32'
Tue Aug 20 14:57:23 2019 daemon.debug [7565]: [/dev/cdc-wdm0] sent message... <<<<<< RAW: <<<<<<   length = 39 <<<<<<   data   = 01:26:00:00:03:02:00:10:00:33:00:1A:00:17:01:00:01:15:08:00:D4:00:16:88:FF:FF:FF:FF:12:08:00:00:00:40:08:00:00:04:10
Tue Aug 20 14:57:23 2019 daemon.debug [7565]: [/dev/cdc-wdm0] sent generic request (translated)... <<<<<< QMUX: <<<<<<   length  = 38 <<<<<<   flags   = 0x00 <<<<<<   service = "nas" <<<<<<   client  = 2 <<<<<< QMI: <<<<<<   flags       = "none" <<<<<<   transaction = 16 <<<<<<   tlv_length  = 26 <<<<<<   message     = "Set System Selection Preference" (0x0033) <<<<<< TLV: <<<<<<   type       = "Change Duration" (0x17) <<<<<<   length     = 1 <<<<<<   value      = 01 <<<<<<   translated = permanent <<<<<< TLV: <<<<<<   type       = "LTE Band Preference" (0x15) <<<<<<   length     = 8 <<<<<<   value      = D4:00:16:88:FF:FF:FF:FF <<<<<<   translated = 3, 5, 7, 8, 18, 19, 21, 28, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 <<<<<< TLV: <<<<<<   type       = "Band Preference" (0x12) <<<<<<   length     = 8 <<<<<<   value      = 00:00:40:08:00:00:04:10 <<<<<<   translated = wcdma-2100, wcdma-800, wcdma-1700-japan, wcdma-850-japan
Tue Aug 20 14:57:23 2019 daemon.debug [7565]: [/dev/cdc-wdm0] received message... <<<<<< RAW: <<<<<<   length = 20 <<<<<<   data   = 01:13:00:80:03:02:02:10:00:33:00:07:00:02:04:00:01:00:03:00
Tue Aug 20 14:57:23 2019 daemon.debug [7565]: [/dev/cdc-wdm0] received generic response (translated)... <<<<<< QMUX: <<<<<<   length  = 19 <<<<<<   flags   = 0x80 <<<<<<   service = "nas" <<<<<<   client  = 2 <<<<<< QMI: <<<<<<   flags       = "response" <<<<<<   transaction = 16 <<<<<<   tlv_length  = 7 <<<<<<   message     = "Set System Selection Preference" (0x0033) <<<<<< TLV: <<<<<<   type       = "Result" (0x02) <<<<<<   length     = 4 <<<<<<   value      = 01:00:03:00 <<<<<<   translated = FAILURE: Internal

Regards,
Nicholas