fix 500 when change user setting email to an exist email (#1039)

Author: lunny

routers/user/setting.go

@@ -105,6 +105,11 @@ func SettingsPost(ctx *context.Context, form auth.UpdateProfileForm) {
 	ctx.User.Website = form.Website
 	ctx.User.Location = form.Location
 	if err := models.UpdateUser(ctx.User); err != nil {
+		if _, ok := err.(models.ErrEmailAlreadyUsed); ok {
+			ctx.Flash.Error(ctx.Tr("form.email_been_used"))
+			ctx.Redirect(setting.AppSubURL + "/user/settings")
+			return
+		}
 		ctx.Handle(500, "UpdateUser", err)
 		return
 	}