Configure BRAT so that if no `.ann` file is found, then an empty `.ann` file is created
I run into the same problem with BRAT from time to time. The way I solved it for a folder with .txt files is to run this Bash one-liner directly in the shell when inside the directory with these files:

for f in *.txt; do touch $(basename $f .txt)".ann"; done


What is does is the following: With a for-loop, it loops over every .txt file, and creates an empty file with touch having the same basename, but a .ann extension instead of a .txt extension.