wireless: fix crash when multi AP used

This is BT: (gdb) bt 0 0x77da2070 in __syscall_ret (r=4294967294) at src/internal/syscall_ret.c:5 1 0x77de5f0c in fstatat (fd=, path=, st=0x7f298140, flag=) at src/stat/fstatat.c:126 2 0x00404bc5 in vlanconf_exists () at system-linux.c:264 3 0x00404bf9 in __device_get.constprop.30 (name=0x9e0060 "wlan1.sta1", create=, check_vlan=) at device.c:662 4 0x0040c8fb in get_vlan_device_chain (ifname=, create=) at vlan.c:274 5 0x00404c0b in __device_get.constprop.30 (name=0x9e0040 "wlan1.sta1", create=, check_vlan=) at device.c:668 6 0x0040c8fb in get_vlan_device_chain (ifname=, create=) at vlan.c:274 7 0x00404c0b in __device_get.constprop.30 (name=0x9e0020 "wlan1.sta1", create=, check_vlan=) at device.c:668 8 0x0040c8fb in get_vlan_device_chain (ifname=, create=) at vlan.c:274 9 0x00404c0b in __device_get.constprop.30 (name=0x9e0000 "wlan1.sta1", create=, check_vlan=) at device.c:668 ... ... 149715 0x0040904f in wireless_interface_handle_link (vif=0x77cef730, ifname=0x790f74 "wlan1.sta1", up=) at wireless.c:330 149716 0x0040c2d9 in wireless_device_hotplug_event (add=true, name=) at wireless.c:1529 149717 device_hotplug_event (name=, add=) at device.c:1226 149718 0x004033c7 in handle_hotplug_msg (size=, data=) at system-linux.c:733 149719 handle_hotplug_event (u=0x42d950 <hotplug_event>, events=) at system-linux.c:749 149720 0x77d6719b in uloop_run_events (timeout=) at uloop.c:198 149721 uloop_run_timeout (timeout=) at uloop.c:555 149722 0x00402c9d in uloop_run () at /home/janusz/iop/ex400/s18/staging_dir/target-mipsel_24kc_musl/usr/include/libubox/uloop.h:111 149723 main (argc=, argv=) at main.c:339

Signed-off-by: Janusz Dziedzic janusz.dziedzic@iopsys.eu