Fix LT-22520: Crash when closing Find dialog in Grammar Sketch (#882)

Author: jtmaxwell3

Src/xWorks/GeneratedHtmlViewer.cs

@@ -228,6 +228,11 @@ private void InitHtmlControl()
 
 		private void Find_Click(object sender, EventArgs e)
 		{
+			if (m_sHtmlFileName == InitialDocument)
+			{
+				// InitialDocument doesn't have the proper javascript for Find to work.
+				return;
+			}
 			findDlg = new FindDialog(m_htmlControl.Browser);
 			findDlg.FormClosing += new FormClosingEventHandler(FindDialog_FormClosing);
 			findDlg.Show(this);