Steps to reproduce

CASE 1

1.  Create a dialog with a Link field without setting showOptions property
2.  Open the dialog and click over the link field

   form:
     properties:
       pageLink:
         label: LINK SHOW OPTIONS
         $type: pageLinkField
   

CASE 2

1. Modify the Dialog to enable showOptions (=true)
2. Open the dialog and click over the link field

   form:
     properties:
       pageLink:
         label: LINK SHOW OPTIONS
         $type: pageLinkField
         showOptions: true
   

CASE 3

1. Modify the Dialog to disable showOptions (=false)
2. Open the dialog and click over the link field

   form:
     properties:
       pageLink:
         label: LINK SHOW OPTIONS
         $type: pageLinkField
         showOptions: false
   

   Expected results

   CASE 1
   The link field doesn't show a drop down list
   CASE 2
   The link field show the list of pages
   CASE 3
   The link field doesn't show a drop down list

   Actual results

   CASE 1, 2 and 3
   Link field shows an empty and black dropdown list