NAN not working for interpolation

[hendrikebbers]

Min/Max/Error values are optional and currently Double.NAN is used for null values when doing interpolation. That ends in an exception:

11:30:06.561 ERROR o.a.c.c.C.[.[.[.[dispatcherServlet]  - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.apache.commons.math3.exception.NotFiniteNumberException: NaN is not a finite number] with root cause
org.apache.commons.math3.exception.NotFiniteNumberException: NaN is not a finite number
	at org.apache.commons.math3.util.MathUtils.checkFinite(MathUtils.java:259)
	at org.apache.commons.math3.analysis.interpolation.LoessInterpolator.checkAllFiniteReal(LoessInterpolator.java:470)
	at org.apache.commons.math3.analysis.interpolation.LoessInterpolator.smooth(LoessInterpolator.java:231)
	at org.apache.commons.math3.analysis.interpolation.LoessInterpolator.smooth(LoessInterpolator.java:394)
	at com.openelements.benchscape.server.store.math.InterpolationUtils.smooth(InterpolationUtils.java:76)
	at com.openelements.benchscape.server.store.endpoints.MeasurementEndpoint.find(MeasurementEndpoint.java:61)
	at jdk.internal.reflect.GeneratedMethodAccessor68.invoke(Unknown Source)