Fix Trix JS Errors When Disabling File Uploads and Clearing Rows

[betsyecastro]

1. Fix ReferenceError in the clear_row() function.

• In Firefox, the error message shows as: Uncaught ReferenceError: assignment to undeclared variable parent_elem.
• Steps to reproduce: on any profile page that has manual edit publications, click on the "Edit" button of the publications section and click on the "x" button in the top right corner of any publication row to remove it.

2. Fix selector errors when disabling Trix file uploads.

• In Firefox, the error message shows as: Uncaught TypeError: can't access property "remove", document.querySelector(...) is null.
• Steps to reproduce: on any profile page that has manual edit publications, click on the "Edit" button of the publications section and click on the "Insert New Item" button located in either the top or bottom section of the page.