don't delete the exiting tooltip if SetToolTip() is called with the same one

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@39146 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/wincmn.cpp

@@ -1526,12 +1526,15 @@ void wxWindowBase::SetToolTip( const wxString &tip )
 }
 
 void wxWindowBase::DoSetToolTip(wxToolTip *tooltip)
+{
+    if ( m_tooltip != tooltip )
     {
         if ( m_tooltip )
             delete m_tooltip;
 
         m_tooltip = tooltip;
     }
+}
 
 #endif // wxUSE_TOOLTIPS