Fixed a crash - Cannot observe a keypath on a weak property.

Author: macmade

ColorSet/Classes/LightnessPairItem.swift

@@ -43,8 +43,8 @@ import Cocoa
 
             super.init()
 
-            let o1 = self.observe( \.lightness   ) { [ weak self ] o, c in self?.update() }
-            let o2 = self.observe( \.base?.color ) { [ weak self ] o, c in self?.update() }
+            let o1 = self.observe( \.lightness ) { [ weak self ] o, c in self?.update() }
+            let o2 = self.observe( \.base      ) { [ weak self ] o, c in self?.update() }
 
             self.observations.append( contentsOf: [ o1, o2 ] )
         }

ColorSet/Classes/LightnessPairWindowController.swift

@@ -32,9 +32,7 @@ class LightnessPairWindowController: NSWindowController
     {
         self.init()
 
-        self.item                = LightnessPairItem( base: base )
-        self.item.lightness1.base = base
-        self.item.lightness2.base = base
+        self.item = LightnessPairItem( base: base )
     }
 
     override var windowNibName: NSNib.Name?

ColorSet/Classes/MainWindowController.swift

@@ -115,6 +115,8 @@ class MainWindowController: NSWindowController, NSTableViewDelegate, NSTableView
 
             self.selectedColor = color
             self.hasVariant    = color.variant != nil
+            
+            self.updateLightnesses()
         }
 
         let o2 = self.observe( \.hasVariant, options: .new )
@@ -136,7 +138,21 @@ class MainWindowController: NSWindowController, NSTableViewDelegate, NSTableView
             }
         }
 
-        self.observations.append( contentsOf: [ o1, o2 ] )
+        let o3 = self.observe( \.selectedColor?.color )
+        {
+            [ weak self ] o, c in self?.updateLightnesses()
+        }
+        
+        self.observations.append( contentsOf: [ o1, o2, o3 ] )
+    }
+    
+    private func updateLightnesses()
+    {
+        for l in self.lightnessPairsArrayController.content as? [ LightnessPairItem ] ?? []
+        {
+            l.lightness1.base = self.selectedColor
+            l.lightness2.base = self.selectedColor
+        }
     }
 
     @IBAction public func performFindPanelAction( _ sender: Any? )