Small fixes on OpenTK support.

Quik.OpenTK/OpenTKPlatform.cs

@@ -37,6 +37,11 @@ namespace Quik.OpenTK
                 IsGLInitialized = true;
             }
 
+            window.Closing += (ea) =>
+            {
+                Environment.Exit(0);
+            };
+
             return port;
         }
 

Quik.OpenTK/OpenTKPort.cs

@@ -72,6 +72,7 @@ namespace Quik.OpenTK
             _vertexEngine.Reset();
             _vertexEngine.ProcessCommands(new QRectangle(), queue);
 
+            if (!_window.Context.IsCurrent)
                 _window.Context.MakeCurrent();
 
             if (!_glDriver.IsInit)