Document and assert that needs_self_check of VexTranslateArgs
must not be NULL.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2207 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/main_main.c b/priv/main_main.c
index 79685a2..9f6379a 100644
--- a/priv/main_main.c
+++ b/priv/main_main.c
@@ -228,6 +228,8 @@
    vex_traceflags = vta->traceflags;
 
    vassert(vex_initdone);
+   vassert(vta->needs_self_check != NULL);
+
    vexSetAllocModeTEMP_and_clear();
    vexAllocSanityCheck();