[Crash] When doing attach pane

function attachPane returns log(    
    pFrm as handle, 
    pNe as handle ):
    /***************************************************************************************
    **
    ** Procedure:       attachPane
    **
    ** Description:     Join a pane to another pane
    **
    ***************************************************************************************/
    define buffer child for child.
    define buffer nchild for child.

    find first child where child.objectHandle = pFrm no-error.
    if not available child then return no.

    find first nchild where nchild.objectHandle = pNe no-error.
    if not available nchild then return no.

    if valid-handle(child.pane) and valid-handle(nchild.pane) then 
    do:
        if (not child.pane:hidden and not nchild.pane:hidden) and (not child.pane:closed and not nchild.pane:closed) then
        do:
	/* Crash at next line */
            chDocMan:DockingPaneFrame:attachPane( child.pane, nchild.pane ).
            debugLog(substitute("Attach pane &1 to &2", child.name, nchild.name ) ).
        end.
        else
            errorLog("Tried to attach to hidden pane").
    end.
    else
        errorLog("ERROR: attach pane - child has become invalid").
end.