metex14: Fix parsing of spaces.

metex14: Fix parsing of spaces.

When the parser found a space, it treated it as an invalid digit
and discarded the whole packet. This behavior was incorrect on
2000 count devices, where the first digit can be sent as a space
rather than a '0'.

Convert spaces to '0' and parse them as usual.

Signed-off-by: Alexandru Gagniuc <redacted>