core/conv: Really only consider error for non-zero soft values

This should have been done with 1dd7c84733b20ba776510369e9daba1a822c5b44
but somehow was missed and only applied to the 'finish' method and
not the 'scan' method.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
1 file changed