Bug fix #34436

Two example files that crashed texture nodes. 
- On delete texture nodes, it should free the exec cache (because this cache
  stores the node pointer.
- On redo, nodes can exist can exist without typeinfo set. Exec (free) code
  was not checking for that. Don't ask me why this happens... tex nodes are weird.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54908 954f8c5b-7b00-dc11-b283-0030488c597c