I have TopComponent without any text components 
in it. It has HelpContext associated with it, 
but when F1 is pressed when this TopComponent is 
active, it is invisible for the help system - 
getHelpCtx() method is never called. 

Here is simple example of that behaviour:

import org.openide.*;
import org.openide.windows.*;
import org.openide.util.*;

public class EmptyTopComponent extends 
CloneableTopComponent{

    public EmptyTopComponent() {
        setName("Empty");
    }    
    public HelpCtx getHelpCtx() {
        System.err.println("Help called");
        return HelpCtx.DEFAULT_HELP;
    }    
    public int getPersistenceType() {
        return TopComponent.PERSISTENCE_NEVER;
    }
}