Bug : parametric mask, picking GUI color from image, chroma channel

dt 3.1.0+2338~g6f9bc02c8, Ubuntu 18.04, OpenCL enabled
Selecting an area from GUI to start defining a parametric mask should initialize the channel sliders with the parameters extracted from the selected area. For the chroma tab I observed a faulty behaviour.
How to reproduce :

  • in darkroom select a module allowing parametric mask
  • CTRL-click on left eyedropper to pick GUI color fom image (area mode)
  • select area from image, tab for L channel is selected, channel slider(s) show corresponding range (OK, screenshot 1) parametric-mask-luminance
  • select tab for channel C, channel slider(s) show range of very low chroma (bug, screenshot 2) parametric-mask-chroma1
  • select tab for channel h, channel slider(s) show narrow blue range (OK, screenshot 3)parametric-mask-hue
  • select tab for channel C again, now channel slider(s) show correct range (OK, screenshot 4)parametric-mask-chroma2

The first time the chroma tab is selected, the range(s) shown in the channel slider(s) are not initialized correctly. One has to switch to tab hue (does not work with tab a or b), then back to chroma tab, to get the correct initialization.