Fixed setting ratio in Transmission

Matches the description in the torrent provider advanced settings:

Left blank defaults to client ratio default.
'-1' Seeds indefinitely
0 or greater seeds to and stops at the ratio (including stopping as soon as it downloads when set to 0)
So you can negative a float, but it can't have a space between the digits and minus sign.

The only condition this doesn't really support is negatives below -1 or random entry. But at least it functions as the description intended.