fix crash in windows launcher

OpenRA.Launcher/JSBridge.cs

@@ -29,8 +29,14 @@ namespace OpenRA.Launcher
 		}
 		Dictionary<string, Download> downloads = new Dictionary<string,Download>();
 
+		readonly Control hostControl;
 		HtmlDocument document = null;
 
+		public JSBridge(Control hostControl)
+		{
+			this.hostControl = hostControl;
+		}
+
 		public HtmlDocument Document
 		{
 			get { return document; }
@@ -177,7 +183,7 @@ namespace OpenRA.Launcher
 					using (var reader = new StreamReader(pipe))
 					{
 						var data = reader.ReadToEnd();
-                        Form.ActiveForm.Invoke((Delegate)(Action)(() =>
+                        hostControl.Invoke((Delegate)(Action)(() =>
                             document.InvokeScript(callbackName, new object[] { data })));
 					}
 				}, url);

OpenRA.Launcher/Launcher.cs

@@ -30,7 +30,7 @@ namespace OpenRA.Launcher
 
 			Util.UacShield(installButton);
 
-			webBrowser.ObjectForScripting = new JSBridge();
+			webBrowser.ObjectForScripting = new JSBridge(this);
 			webBrowser.DocumentCompleted += (o, e) =>
 				{
 					var b = o as WebBrowser;