Correctly handle invalid link threshold on Conquest pages.
Correctly handle invalid link threshold on Conquest pages.

Before wtforms 1.0, invalid numeric fields would still have a `data`
attribute of their default value, but in 1.0 that changed to None.  This
code was assuming `data` was always valid, and trying to do a comparison
to None caused errors in SQLA.

veekun/spline-pokedex,veekun/spline-pokedex,veekun/spline-pokedex