Full value tooltip is shown for empty value

In some cases, a tooltip for an empty value is show: 

To reproduce the problem change in the PropertyGrid sample application do the following steps:

    1. In PrepertyGridDlg.cpp remove/comment xtpGridItemHasEdit flag for "2 Buttons" grid item like this:

    3. Expand "Standard Buttons" category and move the divider so that only 2-3 pixels pixels left between the divider and the "..." button, like this: 

    4. Move mouse over selected part of the line (label) and slowly move it to the right, the tooltip doesn't appear if mouse is moved from the button to the left. At some point, where a mouse cursor still has shape of a movable divider and button is not highlighted yet the empty tooltip will appear.

The problem was encountered with a custom in-place button that occupies all value area - the code is very similar to CCItemButtonControl from the PropertyGrid sample but uses CXTPPropertyGridInplaceButton as a button.

Fix seems to be trivial - add a check for empty string in m_strTipText in CXTPPropertyGridView::ShowToolTip before calling _ShowToolTip.

I would like to get a confirmation/denial for the problem and the fix. And in case of confirmation, I also would like to see the fix in the future versions of the ToolkitPro.

Thank you.