Math Expression nodes cause packaging to fail.

When using a math expression node within a blueprint, the project will fail when packaging.

1. Open editor (any project)
2. In content browser press new>blueprint>actor
3. In event graph add event tick node.
4. In event graph, add math expression node
5. In Math Expression node expression line, type in a+b and press enter.
6. Take delta seconds output from event tick and plug into both a and b.
7. Create print string, plug execution pin from event tick into print string. Plug math expression node output into "in string" input.
8. Compile, save, close blueprint.
9. Package blueprint (File>Package project>Windows>Windows (64 bit)