Looks like you may have leaves turned on when you created your tree but no object assigned as your leaves.
In the Outliner , Top right of the screen, You have the names of your trees. Your currently working on Spruce B.000, just to the left of the name you have a small arrow, click it and everything that makes up your tree will be displayed. See if you have anything named leaves, select it if you do and delete it.
Hope this solves your problem.
Help yourself to a cookie.
