I finally solve the icon problem..
I put the icon image file into "apps" and "hildon" folder..
So i put it in 3 folders in all :

/usr/share/icons/hicolor/scalable/apps
/usr/share/icons/hicolor/scalable/hildon
/usr/share/icons/hicolor/scalable

And after reboot the icon appears, dunno which one made it work..

But i still wonder why does it always crash whenever i'm creating the .desktop file ?