Currently the Function Wizard is broken in that editing a function call
as argument within another function's parameter leads to selections
being reset and mismatching argument/function information being
evaluated. Not sure yet what's going on there, but at least don't access
vectors out-of-bounds or crash.

Change-Id: I633c775556a0b90278d22d0f74d2975c20a08a5d
(cherry picked from commit 88f3c8f9)