Bug fix: Failure when New Tab is clicked while another session is still being loaded

Source commit: 350c582bab706c0d11031f99bbc55be041a3b1d2

source/forms/CustomScpExplorer.cpp

@@ -576,6 +576,7 @@ void __fastcall TCustomScpExplorerForm::SetManagedSession(TManagedTerminal * val
 {
   if (FManagedSession != value)
   {
+    TWindowLock Lock(this);
     SessionChanging();
     DoSetManagedSession(value, false);
   }