fixed. "nothing" is defined as:

    null_actor const nothing = null_actor();
which doesn't make it an actor, rather an "actor base".

Shouldn't it rather be defined as something like:
    actor<null_actor> const nothing = null_actor();

[SVN r51422]

libs/spirit

@@ -1 +1 @@
-Subproject commit 5004d3ddedba4ae39f9075cf2571e4aaf8188530
+Subproject commit f722ef819f7502f02613291626a636b8cc3caff2