fix more -Wparentheses warnings after wxLog changes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61465 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/widgets/listbox.cpp

@@ -448,7 +448,10 @@ ListboxWidgetsPage::GetValidIndexFromText(const wxTextCtrl *text, int *n) const
         // want to retrieve the value as this is only done in answer to a user
         // action
         if ( n )
+        {
             wxLogWarning("Invalid index \"%s\"", text->GetValue());
+        }
+
         return false;
     }