The code would get a pointer to the beginning of the call_args by using
operator[] at the stack Vector. This does bound checking. When there are
no call_args this bound check fails and the error mentioned in #7796
gets triggered.
This bound check is actually not necessary as call_args just gets set to
NULL and never dereferenced. This new code will just unconditionally set
the pointer to the place where the call_args are if there are any. There
is no NULL check for call_args anywhere so this is safe.
Fixes#7796
(cherry picked from commit e8611966de)
