Unbreak utf8clean testcase.

Unbreak utf8clean testcase.

Broken by my compile quitening; the issue was a variable
declared local in a loop body and used for carrying data
from one iteration to the next.  I'd blindly added an
initialiser, destroying the data.  However, I *think* that
compilers might be at liberty to not use the same location
for separate iterations; if so the code was broken (and only
worked by chance).  Fix by moving the declaration outside
the loop.