gtk3: this is why the active position in a menu jumps to some weird place

if there is a reason for this then perhaps it needs to be protected
with pEvent->window == widget_get_window(pThis->getMouseEventWidget()

Change-Id: I714b67c3e6ace932a605dcd00d337c92c5fdfd19
diff --git a/vcl/unx/gtk3/gtk3gtkframe.cxx b/vcl/unx/gtk3/gtk3gtkframe.cxx
index 1695d48..568c4c8 100644
--- a/vcl/unx/gtk3/gtk3gtkframe.cxx
+++ b/vcl/unx/gtk3/gtk3gtkframe.cxx
@@ -2605,18 +2605,6 @@ gboolean GtkSalFrame::signalButton( GtkWidget*, GdkEventButton* pEvent, gpointer
        pThis->CallCallback( nEventType, &aEvent );
    }

    if (!aDel.isDeleted())
    {
        int frame_x = (int)(pEvent->x_root - pEvent->x);
        int frame_y = (int)(pEvent->y_root - pEvent->y);
        if( frame_x != pThis->maGeometry.nX || frame_y != pThis->maGeometry.nY )
        {
            pThis->maGeometry.nX = frame_x;
            pThis->maGeometry.nY = frame_y;
            pThis->CallCallback( SalEvent::Move, nullptr );
        }
    }

    return true;
}