Validate the Mark Older Articles as Read command.

Evergreen/MainWindow/MainWindowController.swift

@@ -127,6 +127,10 @@ class MainWindowController : NSWindowController, NSUserInterfaceValidations {
 			return canMarkRead()
 		}
 
+		if item.action == #selector(markOlderArticlesAsRead(_:)) {
+			return canMarkOlderArticlesAsRead()
+		}
+		
 		return true
 	}
 
@@ -239,7 +243,7 @@ class MainWindowController : NSWindowController, NSUserInterfaceValidations {
 
 	@IBAction func markOlderArticlesAsRead(_ sender: Any?) {
 
-		timelineViewController?.markOlderArticlesAsRead(sender)
+		timelineViewController?.markOlderArticlesAsRead()
 	}
 
 	@IBAction func navigateToTimeline(_ sender: Any?) {
@@ -339,7 +343,12 @@ private extension MainWindowController {
 
 		return timelineViewController?.canMarkSelectedArticlesAsRead() ?? false
 	}
-	
+
+	func canMarkOlderArticlesAsRead() -> Bool {
+
+		return timelineViewController?.canMarkOlderArticlesAsRead() ?? false
+	}
+
 	func updateWindowTitle() {
 
 		if unreadCount < 1 {

Evergreen/MainWindow/Timeline/TimelineViewController.swift

@@ -180,7 +180,7 @@ class TimelineViewController: NSViewController, UndoableCommandRunner {
 		runCommand(markUnreadCommand)
 	}
 
-	@IBAction func markOlderArticlesAsRead(_ sender: Any?) {
+	func markOlderArticlesAsRead() {
 
 		// Mark articles the same age or older than the selected article(s) as read.
 
@@ -207,7 +207,12 @@ class TimelineViewController: NSViewController, UndoableCommandRunner {
 		}
 		runCommand(markReadCommand)
 	}
-	
+
+	func canMarkOlderArticlesAsRead() -> Bool {
+
+		return !selectedArticles.isEmpty
+	}
+
 	// MARK: - Navigation
 	
 	func goToNextUnread() {