Previously, we had a separate match block for script execution. The
motivation was to avoid runtime error due to persistent RefCell
immutable borrow, caused by mozjs mutation.
This PR merge blocks into one. This avoids wildcard match, helping us
identify arms that were never matched, which normally causes error.
Testing: Manually tested. This is one of two ways to avoid panic.
Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>