From 2beeaa513befc905bd74836096ae3d92f12f853e Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 2 Mar 2019 21:27:34 -0500
Subject: [PATCH] Ensures a machine exists before messaging it.

---
 .../xcschemes/Clock Signal.xcscheme           |  2 +-
 .../Documents/MachineDocument.swift           | 28 ++++++++++---------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
index 782b17c09..f9049689f 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
@@ -68,7 +68,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Release"
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"
diff --git a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift
index 2161613e1..c337449f8 100644
--- a/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
+++ b/OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift	
@@ -199,20 +199,22 @@ class MachineDocument:
 
 	// MARK: CSOpenGLViewDelegate
 	final func openGLViewRedraw(_ view: CSOpenGLView, event redrawEvent: CSOpenGLViewRedrawEvent) {
-		switch redrawEvent {
-			case .timer:
-				bestEffortLock.lock()
-				if let bestEffortUpdater = bestEffortUpdater {
-					bestEffortLock.unlock()
-					bestEffortUpdater.update()
-				} else {
-					bestEffortLock.unlock()
-				}
-				self.machine.updateView(forPixelSize: view.backingSize)
-				fallthrough
+		if let machine = self.machine {
+			switch redrawEvent {
+				case .timer:
+					bestEffortLock.lock()
+					if let bestEffortUpdater = bestEffortUpdater {
+						bestEffortLock.unlock()
+						bestEffortUpdater.update()
+					} else {
+						bestEffortLock.unlock()
+					}
+					machine.updateView(forPixelSize: view.backingSize)
+					fallthrough
 
-			case .appKit:
-				self.machine.drawView(forPixelSize: view.backingSize)
+				case .appKit:
+					machine.drawView(forPixelSize: view.backingSize)
+			}
 		}
 	}