Fix for add nodes search box showing nasty "UUUUUUUU"-like entries with some python builds...

Workaround for an issue with python: strings generated by py scripts should also exist in python as long as they are used in C. Else C code may access freed memory.

Simply store the generated list of items in the class, for now. :/

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56191 954f8c5b-7b00-dc11-b283-0030488c597c