don't clear the list control when wxLC_[HV]RULES style is toggled (#4688)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@54201 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/listctrl.cpp

@@ -5123,7 +5123,17 @@ void wxGenericListCtrl::SetSingleStyle( long style, bool add )
     else
         flag &= ~style;
 
-    SetWindowStyleFlag( flag );
+    // some styles can be set without recreating everything (as happens in
+    // SetWindowStyleFlag() which calls wxListMainWindow::DeleteEverything())
+    if ( !(style & ~(wxLC_HRULES | wxLC_VRULES)) )
+    {
+        Refresh();
+        wxWindow::SetWindowStyleFlag(flag);
+    }
+    else
+    {
+        SetWindowStyleFlag( flag );
+    }
 }
 
 void wxGenericListCtrl::SetWindowStyleFlag( long flag )