Avoid throwing an error when Codemirror stateField does not exist
Avoid throwing an error when Codemirror stateField does not exist

Before: https://i.imgur.com/l7rGbGl.png

Bug: none
Change-Id: If7763d71c8a7848695647adc75f5c71579e854f7
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/3361045
Reviewed-by: Tim Van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>
Commit-Queue: Tim Van der Lippe <dba8716ee7f8d16236046f74d2167cb94410f6ed@chromium.org>

ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend