Don't try to update CT clamp's state with NaN values returned from the
underlaying sensor. A single IO error in the sensor code will cause a
NaN to be returned and if we use that in CTClampSensor's floating point
maths both sample_sum_ and offset_ will become NaN and from there every
future calculation will use the NaN offset_ and return NaN too.
Andrew Zaborowski
c8ccb06f11