ColorEdit: Preserve last saturation value when V=0. Disable Hue editing lock.

This workaround is no longer necessary because preserving hue value prevents it from resetting when it is edited in said condition.

imgui_internal.h

@@ -1121,6 +1121,7 @@ struct ImGuiContext
     ImGuiID                 TempInputTextId;                    // Temporary text input when CTRL+clicking on a slider, etc.
     ImGuiColorEditFlags     ColorEditOptions;                   // Store user options for color edit widgets
     float                   ColorEditLastHue;                   // Backup of last Hue associated to LastColor[3], so we can restore Hue in lossy RGB<>HSV round trips
+    float                   ColorEditLastSaturation;            // Backup of last Saturation associated to LastColor[3], so we can restore Saturation in lossy RGB<>HSV round trips
     float                   ColorEditLastColor[3];
     ImVec4                  ColorPickerRef;                     // Initial/reference color at the time of opening the color picker.
     bool                    DragCurrentAccumDirty;