[PATCH] libmm-glib,firmware: fix unique_id checks

[Ben Chan]

The following checks in mm_modem_firmware_select() and
mm_modem_firmware_select_sync() could result in a NULL pointer
dereference if `unique_id' is NULL:

  g_return_if_fail (unique_id != NULL || unique_id[0] == '\0')
  g_return_val_if_fail (unique_id != NULL || unique_id[0] == '\0', FALSE)

This patch fixes the checks to properly verify that `unique_id' is
neither NULL nor an empty string.
---
 libmm-glib/mm-modem-firmware.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libmm-glib/mm-modem-firmware.c b/libmm-glib/mm-modem-firmware.c
index 0bc6c6bd..734b8959 100644
--- a/libmm-glib/mm-modem-firmware.c
+++ b/libmm-glib/mm-modem-firmware.c
@@ -128,7 +128,7 @@ mm_modem_firmware_select (MMModemFirmware *self,
                           gpointer user_data)
 {
     g_return_if_fail (MM_IS_MODEM_FIRMWARE (self));
-    g_return_if_fail (unique_id != NULL || unique_id[0] == '\0');
+    g_return_if_fail (unique_id != NULL && unique_id[0] != '\0');
 
     mm_gdbus_modem_firmware_call_select (MM_GDBUS_MODEM_FIRMWARE (self), unique_id, cancellable, callback, user_data);
 }
@@ -157,7 +157,7 @@ mm_modem_firmware_select_sync (MMModemFirmware *self,
                                GError **error)
 {
     g_return_val_if_fail (MM_IS_MODEM_FIRMWARE (self), FALSE);
-    g_return_val_if_fail (unique_id != NULL || unique_id[0] == '\0', FALSE);
+    g_return_val_if_fail (unique_id != NULL && unique_id[0] != '\0', FALSE);
 
     return mm_gdbus_modem_firmware_call_select_sync (MM_GDBUS_MODEM_FIRMWARE (self), unique_id, cancellable, error);
 }
-- 
2.14.0.rc1.383.gd1ce394fe2-goog