[fixed] (UTF8 string)In outliner,Crashed when preview to UTF8 name image

[tkbd]

How to recreate this problem?

1. Import an image file that contains UTF-8 String.(File name is for example "仔猫画像kitten_img.png")
   
2. Then added an item "仔猫画像kitten_img" into Image category in outliner
   
3. Use "Show" command or double click the item for preview to the image content.
   

Code:

Dump written 2016-12-22_17-45
Version: 2.1.5
Window: wings_outliner
Reason: badarg

Short stack trace:
[]

Long stack trace:
[{io_lib,format,
         ["Image: ~s [~wx~w]",
          [[20180,29483,30011,20687,107,105,116,116,101,110,95,105,109,103,46,
            112,110,103],
           221,203]],
         [{file,"io_lib.erl"},{line,168}]},
{wings_image_viewer,new,3,[{file,"wings_image_viewer.erl"},{line,45}]},
{wings_image,window,1,[{file,"wings_image.erl"},{line,717}]},
{wings_outliner,command,2,[{file,"wings_outliner.erl"},{line,97}]},
{wings_wm,handle_event,3,[{file,"wings_wm.erl"},{line,951}]},
{wings_wm,send_event,2,[{file,"wings_wm.erl"},{line,918}]},
{wings_wm,do_dispatch,2,[{file,"wings_wm.erl"},{line,824}]},
{wings_wm,dispatch_event,1,[{file,"wings_wm.erl"},{line,725}]},
{wings_wm,get_and_dispatch,0,[{file,"wings_wm.erl"},{line,646}]},
{wings,init,1,[{file,"wings.erl"},{line,147}]}]

MacOSX 10.11.6
Wings3D 2.1.5