wimax: i2400m - prevent a possible kernel bug due to missing fw_name string

This happened on a machine with a custom hotplug script calling nameif,
probably due to slow firmware loading. At the time nameif uses ethtool
to gather interface information, i2400m->fw_name is zero and so a null
pointer dereference occurs from within i2400m_get_drvinfo().
Signed-off-by: Phil Sutter <phil.sutter@viprinet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wimax/i2400m/netdev.c

@@ -597,7 +597,8 @@ static void i2400m_get_drvinfo(struct net_device *net_dev,
 	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
 
 	strncpy(info->driver, KBUILD_MODNAME, sizeof(info->driver) - 1);
-	strncpy(info->fw_version, i2400m->fw_name, sizeof(info->fw_version) - 1);
+	strncpy(info->fw_version,
+	        i2400m->fw_name ? : "", sizeof(info->fw_version) - 1);
 	if (net_dev->dev.parent)
 		strncpy(info->bus_info, dev_name(net_dev->dev.parent),
 			sizeof(info->bus_info) - 1);