Ignore mqtt incoming value

when i turn on or off my mqtt color switch it sends “undefined,undefined,undefined” as the color value so i get a log error like

[WARN ] [ab.binding.mqtt.generic.ChannelState] - Command 'undefined,undefined,undefined' from channel 'mqtt:topic:b94727f5:nspanel:nscolor' not supported by type 'ColorValue': For input string: "undefined"

what tranfomation can i use to ignore only this value?

E.g. regex and look for a numeric pattern

I out this in the incoming transformations value in the advanced section of the thing . For example:

REGEX:(.*HSBColor.*)∩JSONPATH:$.HSBColor

You have to have the regex addon installed as well.