Code fine in 4.0 and driving me crazy in 5.0

Question

I started what I thought was going to be a really quick change in 5.0, since it has already been done in our 4.0 webclient. 
In the activity clipboard under the column activity, I want to just change the text "customer" to say "contact".   This is what I did in 4.0 and everything is fine.  In 5.0 I bomb. 
I created a z version of the controller. 
ZL_CRM_IC_IRECACTIVITIESC_IMPL of course with the correct superclass.   A Z version of the iterator
zl_crm_ic_irecactivitiesc_it with a superclass.
I redefined SET_MODELS of the z IMPL and replaced
IF NOT iterator IS BOUND.
    CREATE OBJECT iterator TYPE Cl_crm_ic_irecactivitiesc_it.
ENDIF.
With
IF NOT iterator IS BOUND.
    CREATE OBJECT iterator TYPE Zl_crm_ic_irecactivitiesc_it.
ENDIF.
In the new version of the iterator.  I redefined
IF_HTMLB_TABLEVIEW_ITERATOR~RENDER_CELL_START
under the first when my code looks like this
        when gc_colkey_activity.
          if line_ref->a_text eq 'Customer'.
            zpartner = line_ref->m_text.
            length = strlen( zpartner ).
            compute length = 10 - length.
            while count lt length.
              concatenate '0' zpartner into zpartner.
              add 1 to count.
            endwhile.
            clear count.
            select single * into ZBUT100 from BUT100
                  where partner = zpartner.
            if zbut100-rltyp = 'BUP001'.
              line_ref->a_text = 'Contact'.
            endif.
          endif.
          p_replacement_bee = me->process_cell( iv_id      = p_cell_id
                                                iv_col_bee = gv_activity
                                                iv_link    = line_ref->activity-link
                                                iv_text    = line_ref->a_text ).
In debug mode, I go into process_cell and dump on this line
iv_col_bee->id        = iv_id.
iv_col_bee->reference = iv_link.
iv_col_bee->text      = iv_text.
This is exactly what I have in 4.0 and did pretty much the same thing in servitemlist.  What am I missing.  I'm sure I'm just over looking something.
Thanks,
Cat

Answer 1

Patrick,
  Thanks for responding.  This is what ST22 says.  The only difference between 4. and 5.0 is that when I extended the iterator in 4.0,  the only attributes I had to define were the constants GC_COLKEY_ACTIVITY, GC_COLKEY_DESCRIPTION, GC_COLKEY_MOREINFO. 
The other attributes were defined as public or protected.  In 5.0 I also had to define GV_BLANK_BEE, GV_ACTIVITY,
GV_DESCRIPTION, GV_MOREINFO, because they were defined as private and not protected.  Same thing with Methods GET_BLANK_BEE and PROCESS_CELL.  The problem has to be somewhere in how I'm calling PROCESS_CELL or in PROCESS_CELL.  I'm just not experience enough to know if something should say me-> or not  Here the dump info below. 
  You attempted to use a 'NULL' object reference (points to 'nothing')
  access a component (variable: " ").
  An object reference must point to an object (an instance of a class)
  before it can be used to access components.
  Either the reference was never set or it was set to 'NULL' using the
  CLEAR statement.                                                                               
THE LINE IT POINTS TO IS
method PROCESS_CELL.
field-symbols: <linktype> type string.
                                                                                if iv_text is initial or
     iv_link is initial or
     iv_link = iv_alink.             "Only create link in 2nd/3rd column if differ
    gv_blank_bee->id   = iv_id.
    gv_blank_bee->text = iv_text.
    rv_result          = gv_blank_bee.
  else.
                                                                                iv_col_bee->id        = iv_id.
    iv_col_bee->reference = iv_link.
    iv_col_bee->text      = iv_text.
  Attribute LinkType no available in all basis SPs - use dynamic assignment*
    assign iv_col_bee->('LINKTYPE') to <linktype>.  "#EC NOTEXT
    if <linktype> is assigned.
      <linktype>  = 'INITIAL'. "#EC NOTEX
    endif.
  endif.
                                                                                endmethod.