Don't release capture unless we already have it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31826 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/popupcmn.cpp

@@ -198,7 +198,8 @@ void wxPopupTransientWindow::PopHandlers()
             m_handlerPopup = NULL;
         }
 
-        m_child->ReleaseMouse();
+        if (m_child->HasCapture())
+            m_child->ReleaseMouse();
         m_child = NULL;
     }