Fix warnings introduced in Xcode 9

ColorPicker/ColorPicker.framework/Versions/A/Headers/CPKColorWell.h

@@ -13,10 +13,10 @@
 @property(nonatomic, assign) BOOL noColorAllowed;
 // Called just before popover opens.
-@property(nonatomic, copy) void (^willOpenPopover)();
+@property(nonatomic, copy) void (^willOpenPopover)(void);
 // Called just before popover closes.
-@property(nonatomic, copy) void (^willClosePopover)();
+@property(nonatomic, copy) void (^willClosePopover)(void);
 // Override these methods to customize how the popover is presented. Normally it is presented from
 // the color well's frame.

ColorPicker/ColorPicker.framework/Versions/A/Headers/CPKMainViewController.h

@@ -31,7 +31,7 @@ typedef NS_OPTIONS(NSInteger, CPKMainViewControllerOptions) {
                  alphaAllowed:(BOOL)alphaAllowed DEPRECATED_ATTRIBUTE;
 - (instancetype)initWithBlock:(void (^)(NSColor *))block
-         useSystemColorPicker:(void (^)())useSystemColorPickerBlock
+         useSystemColorPicker:(void (^)(void))useSystemColorPickerBlock
                         color:(NSColor *)color
                       options:(CPKMainViewControllerOptions)options;

ColorPicker/ColorPicker.framework/Versions/A/Headers/CPKPopover.h

@@ -13,7 +13,7 @@
 @property(nonatomic, strong) NSColor *selectedColor;
 /** Called before popover closes. */
-@property(nonatomic, copy) void (^willClose)();
+@property(nonatomic, copy) void (^willClose)(void);
 /**
  * Shows the color picker in a popover. Returns the semitransient popover.
@@ -39,6 +39,6 @@
                          initialColor:(NSColor *)color
                               options:(CPKMainViewControllerOptions)options
                    selectionDidChange:(void (^)(NSColor *))block
-                 useSystemColorPicker:(void (^)())useSystemColorPicker;
+                 useSystemColorPicker:(void (^)(void))useSystemColorPicker;
 @end