It's not important whether null or not, as long as it properly detects
that no threshold is set. Further tests specifically for ThresholdRange
should accommodate this case by verifying we don't detect any WARNING.
refs #1298
key=23;0;0;0;0 and key=23;;;; lead to division by zero exceptions
This should fix this by ignoring empty strings for min/max (formerly
it got "converted" to float(0)) and also ignores min == max.
fixes#6828
Prior to this change the PerfdataSet only knew the labels of a performance
data value which prevented the Perfdata object from being used
individually.
refs #6515
Johannes Meyer
Alexander A. Klimov
Eric Lippmann
Thomas Gelf
Johannes Meyer
Matthias Jentsch