#33 null pointer exception when deleting whole graph.

[Joseph Coffland]

Selecting everything in the graph editor and pressing
delete caused a null pointer exception and incomplete
deletion. This is likely related to the node in the
new graph.active variable be deleted and then accessed
as the selection changes. This may be a SinaXe error
or may be in the YMLEditor's SinaXe markup.

Reloading or reverting the project should solve the
problem.