As described by JazzyNico, this is rather tedious to reproduce with local builds on OS X (tested with lp:inkscape/0.92.x, GTK+/X11 2.24.29 and GTK+/Quartz 2.24.30), and happens rarely in regular usage.
I have not been able to reproduce it with Inkscape 0.91 at all - it might be possible that this behavior originates in or was exposed by changes from the merge of the fill-n-stroke-cppify (r14160) - I recall that after the merge I started to notice occasionally a defunct fifth slider displayed in some of the color modes (not persistent).
As described by JazzyNico, this is rather tedious to reproduce with local builds on OS X (tested with lp:inkscape/0.92.x, GTK+/X11 2.24.29 and GTK+/Quartz 2.24.30), and happens rarely in regular usage.
I have not been able to reproduce it with Inkscape 0.91 at all - it might be possible that this behavior originates in or was exposed by changes from the merge of the fill-n- stroke- cppify (r14160) - I recall that after the merge I started to notice occasionally a defunct fifth slider displayed in some of the color modes (not persistent).