Initialize m_isShown correctly in wxGenericDragImage::BeginDrag().

The code initialized m_isDirty twice which was clearly wrong. The original
intention was probably to set both m_isDirty and m_isShown to false.

Thanks to PVS-Studio for finding this bug.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70749 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/dragimgg.cpp

@@ -247,7 +247,7 @@ bool wxGenericDragImage::BeginDrag(const wxPoint& hotspot,
         m_boundingRect = * rect;
 
     m_isDirty = false;
-    m_isDirty = false;
+    m_isShown = false;
 
     if (m_cursor.IsOk())
     {