The default float IDProperty min value rB8b9a3b94fc148d19 for when there
is no UI data was FLT_MIN instead of -FLT_MAX, which meant that animated
custom property values couldn't be less than zero unless they had their
UI data values edited previously.
That's a mistake I won't make again! Also change the int minimums from
-INT_MAX to INT_MIN to sanitize the whole situation.
276a862ebc