[PATCH libinput v2] Fix an abort if the device speed is NaN

[Bill Spitzak]

On 02/05/2015 05:33 AM, Olivier Fourdan wrote:
> When using libinput with xf86-input-libinput, the device speed is
> represented as a float passed via X properties.
>
> If a buggy client gives a broken value, the conversions that occur
> can cause the value of speed to be NaN (not a number), aka infinity.

Actually NaN is *not* infinity. ±Infinity would both return the expected 
values from the older if statements.

The fix looks correct to me however.