Description

Steps to reproduce:

1. Go to https://wikifunctions.beta.wmflabs.org/wiki/Z10112?view=default-view&action=edit
2. Clear the content and type by doing:
   • Instead of "Type: Mushroom" select "Type: Reference"
   • Instead of "Type: Reference" select "Type: Object"

Observed behavior:

• When focusing on the empty selector "Select a Type", it expands up to 223px instead of fitting the whole screen
  

• When "debug=true", the item shows correctly (expands to 100% of the page). When the debug param is not present is when this error shows.

Expected behavior (Acceptance criteria):

• The field expands to cover the 100% of the available space, like the others:
  

Completion checklist

• Before closing this task, review one by one the checklist available here: https://www.mediawiki.org/wiki/Abstract_Wikipedia_team/Definition_of_Done#Front-end_Task/Bug_Completion_Checklist