preventing from clicking Accept without choosing file annotation (rebased onto develop)



This is the same as gh-2780 but rebased onto develop.

----

This fixes https://trac.openmicroscopy.org.uk/ome/ticket/12266

You should no longer be able to click Accept without previously choosing new or existing file annotation. To test play with the form and see if there is any case "No Files Chosen" appears on the Annotation list.